Smith has almost single-handedly carried his side’s batting burden in this series, despite sitting out at Headingley with concussion, and reached lunch on 101 not out.
That followed his previous scores of 144, 142 and 92 – a sequence that might ultimately prove to be the difference in the two sides’ battle for the urn.
Smith resumed on 60 and rode out a tricky start, during which Jofra Archer failed to claim a return catch, to score another 41 runs in 70 balls.
Australia added 75 for two in the opening session, Travis Head and Matthew Wade proving considerably easier pickings than the relentlessly obdurate Smith.
England, though, will surely reflect that they missed out in the first 20 minutes.
Stuart Broad got the better of him with the first two balls of the day, a thick edge landing in front of the cordon and missing entirely with an ugly swipe outside off stump.
Archer kept the pressure on at the other end, drawing another play and miss in the channel.
He should have had Smith for 65 with his third delivery, a low full toss which was pushed straight back at the seamer. It appeared to be a relatively simple caught-and-bowled but Archer failed to get a firm hand on it and a golden opportunity for England turned into four runs for Australia.
Smith was being challenged, Archer drawing an inside edge that squirmed into the leg-side and then testing him with a more threatening bouncer than any he had managed on day one, but each minute that he spent in the middle seemed to reduce the bowler’s advantage.
An effortless steer to the third man boundary off Broad suggested he was finding his feet once again and he soon began to accumulate effortlessly.
England were able to put an end to Head’s sketchy innings of 19, Broad’s round-the-wicket angle to left-handers racking up another victim as he picked up his second lbw of the Test and 17th wicket of the series.
Wade was next to abandon Smith, making a deeply unconvincing 16 before racing down the pitch in a bid to smash Jack Leach over the top. Instead of the mighty connection he envisaged the ball soared skywards and eventually dropped into Joe Root’s hands at mid-on, notwithstanding a few nervy moments as the England captain waited underneath.
Smith moved to 99 with 10 successive singles and then flicked Craig Overton to midwicket for two to bring up his 26th Test century, 11 of which have come against England.