Kane made it 3-0 20 minutes after the restart when he squeezed a rebound in at the near post having seen his initial shot saved by Francioni.
The Tottenham Hotspur starlet then completed his hat-trick in the closing stages as he latched on to a clever pass from Tom Carroll before rounding the keeper and sliding the ball into the empty net.
You can read how a comfortable win for England unfolded with Sports Mole's live coverage below.
7pmGood evening! Thank you very much for joining Sports Mole for tonight's game as San Marino Under-21s host England Under-21s in Serravalle. It looks like being a straightforward match for England on paper, but San Marino will, unusually, be full of confidence.
7.02pmThat confidence is born out of an incredibly rare win for the international minnows, who beat Wales Under-21s 1-0 in their last outing. It was a devastating and embarrassing defeat for England's neighbours, but it is hard to begrudge San Marino getting any sort of a result considering how rare it is.
7.04pmThe win was their first victory in 31 matches, a run that stretches all the way back to May 2006, more than seven years ago. That day they beat Armenia U21 3-0 in a historic day for the country's footballing youth.
7.06pmIn the 30 matches between their last two wins, San Marino have shipped more than five goals in a match no less than 13 times, with the nadir coming in an 11-0 defeat to Germany in 2009. It wasn't like they were scraping draws in this time either - a goalless stalemate against Greece last year was the only time that they didn't lose one of those matches, leaving their record over the past seven and a half years as P31 W1 D1 L29.
7.08pmThere isn't much to be said in Wales's defence but San Marino have improved recently, especially in terms of goals conceded. The last time they were on the end of a real battering was exactly two years ago today, when Germany beat them 8-0. Their record since then hasn't been great by any stretch of the imagination, but they have limited the opposition to two goals or less in all but two of their matches since then.
7.10pmUnsurprisingly, San Marino currently sit bottom of Group 1 after four matches. They have already surpassed their usual points tally in a campaign, however, and are just one point behind England in the group. Overall, in their European Championships qualifying history, San Marino have played 86 games, winning just three, drawing one and losing the remaining 82. In that time they have scored just 26 goals and conceded a whopping 352, leaving their overall goal difference at -326.
7.12pmSo, what could possibly go wrong for England? Well, anything less than a substantial win tonight would go down as a disappointment for England, who are still getting used to life under Gareth Southgate. They have played two games under the former Middlesbrough boss, winning their opening match against Moldova 1-0 before playing out a 1-1 draw with Finland.
7.14pmSouthgate took over the job from Stuart Pearce after a disastrous European Championships campaign in the summer. The Young Lions lost to Italy, Norway and hosts Israel on their way to a bottom-placed finish in their group, ending the tournament without a point - and just one goal - to their name.
7.16pmIt certainly hasn't been a spectacular start for Southgate, but it has been a steady one. Tonight should be a chance to improve their goal difference significantly and, although Southgate has previously said that performances are more important than results in the early days, not winning here is nigh-on unthinkable for England.
7.18pmTEAM NEWS: Time to bring you some team news, and there are some interesting selections, and non-selections, by Southgate. In-form Ravel Morrison is handed his his debut, as is Carl Jenkinson who, of course, has already played for the full side on one occasion. Another player who has featured for the senior side is Wilfried Zaha, but he is only on the bench tonight, as is Saido Berahino, who has made such a good start to his Under-21 career and is in good form for club side West Brom.
7.25pmPREDICTION: This is one of the easier matches I've ever had to predict. San Marino's win over Wales may cause a tiny element of doubt to creep into people's heads, but this should be a walk in the park for England tonight. Southgate hasn't named his strongest starting lineup possible, but there should still be goals. I'm going for 5-0 to England.
1 minKICKOFF: Here we go, then. San Marino get us underway as they look to make it an unprecedented two wins in a row against England. Any result today would surely be the biggest in their history.
3 minBright start from England as the ball is lifted towards Morrison inside the box, but Manzaroli is out well to claim, picking up a knock for his efforts.
5 minAn early breakthrough for England, and it is just what they would have wanted. It isn't the prettiest goal as the ball bounces around in the box with a suspicion of handball against Sterling in the midst of it all, but finally Keane finishes the scramble with a finish from close range.
9 minThis may be a long night for San Marino if the first 10 minutes is anything to go by. As expected, the visitors have dominated possession early on and have not been troubled defensively at all. Expect damage limitation from San Marino throughout.
12 minSterling wins a free kick in a good position but Kane chooses to take it quickly, playing a short pass to the Liverpool man who is stopped in his tracks when trying to weave his way into the box.
14 minEngland's goal came from a corner won by Thomas Ince, by the way. He skipped past the keeper but was forced too far out wide to shoot, so instead chose to cross. The San Marino defence was well placed and put it behind for the corner that ultimately led to the opening goal.
15 minLiverani whips a free kick into the box and, to be fair, San Marino have committed a decent amount of men forward. The cross is disappointing, however, and Butland is able to comfortably collect.
17 minCHANCE! Nice play from Sterling down the right as he races away from his man before looking to find the far corner from a fairly tight angle. He may have been better served looking for a teammate there, but his effort wasn't too far off and he will be forgiven for being selfish in games like this.
19 minSterling looks like he has been given a free role this evening. He picks the ball up in the middle of the park this time before disguising a pass to Ince, who just can't get the ball under control before the defence clears.
21 minYELLOW CARD! Wow, that is one of the worst refereeing decision I have seen in a while. Sterling is causing problems again, this time on the left wing, and he races past a couple of players before clearly being brought down by a poor challenge. The ref, however, gives the free kick the other way and books Sterling for diving! Terrible decision.
22 minThen, moments later, a clear dive from a San Marino player goes unpunished. Very odd refereeing.
25 minStill just the one goal for England but the second looks inevitable, it is just a question of when they will get it. Sterling has been the man causing most problems at the moment and he looks the most likely route to another goal.
26 minYELLOW CARD! San Marino pick up their second yellow card of the night as Muraccini brings down Carroll. The hosts are conceding a lot of free kicks in their attempts to stem the tide here.
28 minThe ball is played back to Carroll, who takes it off the toes of Morrison on the edge of the box before going for goal himself. His effort is deflected on the way through, taking it wide for another corner.
30 minCHANCE! What a chance that is for Sterling! Ince shows good skills and footwork to reach the byline down the right before clipping the ball back into the middle where red shirts are queuing up the shoot. The keeper is in no-man's land and it should be an easy finish for the Liverpool man, but he nods it over the bar. Even accounting for his lack of aerial prowess, that was a huge chance.
32 minAnother half chance for England, and this time it falls to Ince. A long ball over the top beats the entire San Marino defence and Ince is clear through on goal, but he just can't get full control of it until it is too late, allowing the defence to get back and momentarily clear the danger.
34 minCHANCE! I'm not quite sure how this is still only 1-0! England should have a second here as Sterling leads a counter-attack, beating his man with sheer pace on the right before playing an early ball across the box to Ince. The bounce makes it a little difficult for him, but he still should do better as he puts it over the bar under no pressure.
36 minThe only thing that has been missing for England at the moment is finishing. They have created plenty of chances and should be at least three or four up, but still it remains just 1-0.
38 minCHANCE! Another fine opening for the visitors goes begging. It is another counter-attack as San Marino commit men forward for a free kick that is comfortably dealt with. The ball is floated over to Ward-Prowse, unmarked on the edge of the box, but his first touch is poor and allows the keeper to come out and claim. It was decent goalkeeping from Manzaroli, who was brave, but Ward-Prowse should have never given him the chance to get that ball.
40 minInce spins away from his man and finds space to shoot from 25 yards out, but his effort is deflected out for yet another England corner. Can they make more of this one?
41 minNo. It is once again cleared before England launch another attack which end with Morrison slicing a shot wide from a similar position to the Ince effort just a minute ago. England are trying more long shots now, which is perhaps a sign of growing frustration.
43 minTo be fair to England, San Marino are playing with a back nine at the moment, crowding out the middle of the park and not giving the visitors any room to work with. Sterling managed to wriggle into some space just then, but his attempted through ball to Jenkinson was just too heavy.
44 minThe referee blows for another dive by an England player, and this time he looks to have got the decision right. Stones played Ince in down the right and the Blackpool man went past his man before throwing himself to the ground when he realised that he wouldn't get the ball before it went out for a goal kick. There may have been minimal contact, but it wasn't enough to warrant a penalty. Strangely, while Sterling was booked earlier, Ince isn't here.
45 minRED CARD! Andrea Manzaroli (San Marino U21s)
45 minWell, if San Marino were up against it before, they surely have no chance now. Ince plays the ball into the box for Sterling to run on to, and he gets there at about the same time as Manzaroli. The Liverpool man goes down under the challenge and the referee promptly points for a penalty and shows the keeper the red card. Both players seemed to get a bit of the ball there, so it was a harsh decision.
45+3 minGOAL! San Marino U21 0-2 England U21 (Harry Kane)
45+3 minOn comes sub keeper Francioni in place of Liverani, and his first action is to pick the ball out of the back of his net. Harry Kane is the man to step up to the spot kick and he makes no mistake as his effort goes in off the right hand post. It is now 2-0 to England against the 10 men of San Marino.
45+3 minHALF TIME: San Marino U21s 0-2 England U21s
8.24pmWell, what a dramatic end to the first half that was. Kane's spot kick was the last action of the half as England finally find the second goal that, in truth, they should have scored a long time ago. As expected, Southgate's men have dominated this match and the only surprise is that it is only 2-0.
8.26pmSan Marino have a long 45 minutes ahead of them. They looked to be going into half time just 1-0 down, which would have pleased manager Pier Angelo Manzaroli no end given England's dominance. Now, after that nightmare couple of minutes at the end of the half, they are 2-0 down and must play the rest of the match with just 10 men. If they can keep the score to anything lower than 5-0 here, they will have done well.
8.28pmI've just seen that penalty again, and as it happens it didn't come off the post but instead off the keeper's hands. It was not a good penalty from Kane, who fired it straight down the middle, and Francioni really should have saved it to be honest. What a first action of the match that would have been for the sub keeper. Kane, meanwhile, is a lucky man.
8.30pmEngland took the lead early one through Michael Keane following a goalmouth scramble from a corner, but the main talking point of the half will be that late penalty. The award of it was suspect as both Manzaroli and Sterling seemed to touch the ball at the same time. It was not a penalty, in my opinion, but also not a dive from Sterling, who has already inexplicably been booked for simulation when he was clearly fouled.
8.31pmIn truth, this referee has had a shocker in the first half. He has got most of the decisions wrong, including that Sterling one which almost defied belief. The penalty will be the biggest one, of course, but it is by no means his only mistake of the match. Even when he has got a decision right, such as turning down a penalty claim from Ince and instead awarding a free kick for diving, he failed to show consistency by not brandishing a card like he did for Sterling.
8.33pmThere was even a hint of controversy about England's opening goal as the ball appeared to strike a hand in the goalmouth scramble that preceded Keane's strike. However, despite both goals carrying an air of controversy about them, there is absolutely no doubt that England deserve to be winning this match. They have squandered a whole host of glorious chances, with Sterling and Ince being most culpable. Having said that, they are the two players who have caused most problems for San Marino so far as they struggle to deal with their trickery and sheer pace.
8.34pmFrancioni, the keeper who has just come on as a sub, has been out on the pitch for the entire half-time period, catching balls and getting warmed up. He is going to have a busy half ahead of him, you feel.
46 minKICKOFF: We're back underway in Serrevalle as England looks to build upon their two-goal lead. It is the visitors who kick us off for the second period, with no changes for either side at the break.
48 minGood chance early in the half for England after Stone's initial low cross is cleared away. The ball is then floated perfectly over the head of the last defender with Kane waiting at the back post, but he can't control it as the ball squirms away from him. A good first touch there would have presented him with a really good chance.
49 minOFF THE POST! England almost increase their lead in very fortuitous circumstances. Stone beats his man down the right with a hint of a body swerve and sheer pace before mis-hitting a cross into the middle. The ball looks like it is going to creep in at the near post, with the keeper nowhere to be seen, but instead it comes off the outside of the upright and out for a goal kick.
51 minSAVE! Yes, yet another chance for England goes begging. Kane competes for a cross in the middle of the box and causes enough confusion to ensure that the defence can't clear. It falls to Morrison a couple of yards inside the area, and he fakes a shot before looking to pass the ball into the bottom corner, but the keeper gets down well to make the save. He should have scored there.
53 minYou get the feeling that England are looking to play party football due to the weakness of the opposition. In the Premier League, Morrison probably would have lashed that into the roof of the net, giving the keeper no chance. Here, however, he tried to make the finish look easy and, as a result, missed what was a glorious chance for a goal on his debut.
55 minCHANCE! There is some more party football from Morrison, but this time it comes off. He produces a lovely backheel into the box where Carroll is waiting, but the keeper is out well to smother his shot. The ball bounces out to Stones on the edge, but his first-time effort is high and wide with most of the goal to aim at.
56 minENGLAND SUB: That nice little backheel was Morrison's last action as he is replaced on his debut by Jesse Lingard.
58 minGREAT SAVE! This is getting harder and harder to believe that it is only 2-0. Kane is the latest to miss a glorious chance as he gets on the end of Ince's inch-perfect cross to head towards goal from close range. Francioni makes a very good stop to deny the striker, but Kane still really should have scored. If he hit that anywhere but straight at the keeper, it would be 3-0 right now.
60 minOverall, Francioni has had quite a good second half so far. He has certainly been busy, but he has been up to the task of keeping England at bay so far. He has some poor finishing to thank as a couple of the chances should have been scored regardless of who was in goal, but he deserves some credit for sure.
62 minCarroll drills a powerful cross into the box that Francioni gets a hand to at the near post. I'm not sure he knows much about it, but he will be relieved to see if fall at the feet of his defenders who, eventually, are able to clear.
63 minEngland's latest in a long line of corners is flicked on at the near post but it lands just out of the reach of Sterling at the far stick before going out for a goal kick.
64 minJenkinson makes a marauding run down the left but it is ultimately a wasted one as he tries to shoot from a very tight angle when he had men in support inside the box. He slices his half-volleyed effort well wide.
65 minGOAL! San Marino U21 0-3 England U21 (Harry Kane)
65 minAt long last England have their third goal. Kane did his best to miss this one but eventually managed to squeeze it in, although Francioni can feel hard done by. Sterling played a defence-splitting pass through to the striker, who was one-on-one with the keeper but produced a poor first shot that Francioni was able to save. He couldn't hold on to it, however, and Kane poked the rebound in at the near post.
67 minENGLAND SUB: Sterling has had a fine evening tonight, even with that missed chance in the first half. His match is over, however, as Danny Ings comes on for his debut. He has been in fine form for his club this season, so it will be interesting to see whether he can carry that form over to international matches. He won't get many better chances to score than today.
69 minYou might as well add Jack Butland to the meagre amount of spectators watching this match. The skipper for the night in Andre Wisdom's absence has had very little to do, and has not been in the match at all in this second half.
71 minYELLOW CARD! Colombini enters the referee's book, and it is quite a harsh free kick in the first place. The skipper appeared to get the ball, but I think it was his angry reaction more than the foul that prompted the referee to book him.
73 minENGLAND SUB: There will be no rest for the San Marino defence as the exciting Nathan Redmond comes onto the field. He has made a fine start to his Norwich career and can really torment defences when on form.
75 minI thought the referee was about to book Stones for kicking the ball away there. The defender simply tapped it to one side after the whistle was blown but the ref ran over full of purpose before speaking to his linesman and decided against brandishing another card.
77 minCLOSE! Kane is searching for his hat-trick here and almost gets it with a snapshot from the edge of the box. He doesn't really catch it right and it bobbles past the far post, but it was not far away.
79 minSome of the sting has gone out of the England attack since Sterling went off, it must be said. They are still dominating the match but it has been a while since they had a really good chance on goal. In fact, their last clear opening was the third goal, shortly after which Sterling was withdrawn.
81 minDecent opening for Redmond there, but again the finish is disappointing. The winger had space on the edge of the box but dragged his shot well wide when he should have at least tested the keeper.
83 minTo be honest, both sides look fairly happy with this scoreline at the moment. England aren't exactly busting a gut to add to their tally, while San Marino are still in the same damage limitation mode that they have been in since the first whistle.
85 minFrancioni comes out to punch a corner and, although he gets to the ball amid a mass of bodies, the clearance is by no means convincing. It falls straight to Redmond on the edge of the box, but the Norwich man is lacking urgency and his eventual shot is probably the tamest of the day so far as it trickles into the keeper's arms.
87 minThis will be a very comfortable three points for England, but I must say that it is a little disappointing that they haven't been more adventurous. They should be beating this San Marino side by six or seven goals, but they look content with a 3-0 win. In fairness, they have created enough chances to win by a bigger margin, but some of the finishing from England today has been poor.
88 minGOAL! San Marino U21s 0-4 England U21s (Harry Kane)
88 minJust as I say that, England go and score a beautifully-worked goal. Carroll played a lovely scooped ball over the top of the defence for Kane to run on to, and he took it past the keeper before finishing well from a tight angle. It is a hat-trick for him, and he could have easily had more too.
90 minVery nearly five in the closing stages as a low ball into the box from Stones eludes three red shirts sprinting in to add the finishing touch. I think it was Kane again who got closest, missing the ball by a matter of inches.
90+3 minKane does have the ball in the back of the net for a fourth time after another long ball beat the entire defence once again, but this time Kane did not beat the offside trap. He knew he was off as he coolly slotted the ball home.
90+3 minFULL TIME: San Marino Under-21s 0-4 England Under-21s
9.26pmThere you have it! England move up to second in their qualifying group for 24 hours at least with a comfortable 4-0 win over the minnow of San Marino. Harry Kane will steal the headlines with a hat-trick but it was a good performance from most of the players tonight, except when it came to finishing. Michael Keane got the Young Lions' opening goal from close range, while the hosts were reduced to 10 men at the end of the first half.
9.28pmSan Marino may have lost 4-0, but they won't be too down tonight. They will know as well as anyone that it could, and should, have been an even bigger win for England. Still, the hosts deserve credit for keeping the score down against a much better side having had to play half of the match with a man less after their keeper was sent off. The result was never really in doubt, but San Marino will be pleased with their resilience.
9.30pmRight, that's just about all we have time for this evening. Thank you very much for joining Sports Mole for what was a comfortable win for England, although I'm sure they would have liked to have won by more than the four-goal margin. I will leave you with our match report, and be sure to stick around for analysis, which will be up within half an hour. The senior England side are in action tomorrow along with a whole host of other games in the World Cup qualifying campaign, so come back then when we will have it all covered. Until then, though, it is goodbye!