The captain had already ensured his 100th Test cap would be fondly remembered after reaching three figures on day one, but his appetite showed no signs of abating as he reached an unbeaten 209 on the second afternoon in Chennai.
Eight other men have marked their hundredth appearance with a century, but nobody in the history of the game ever gone this far before. Yet, having posted scores of 228 and 186 in his previous two outings in Sri Lanka last month, there is a growing sense of inevitability about Root's mammoth scoring.
With Ben Stokes contributing a bullishly aggressive 82 on his return to the side after six months away, England were in a dream position at tea.
Root had been happy to play second fiddle in the first session, handing his partner the baton as he spent two hours adding a modest 28 to his overnight score. Stokes narrowly survived a vicious yorker from Jasprit Bumrah while still on nought before revealing his first two scoring shots, steering the paceman for four between slip and gully then a lifting Ravichandran Ashwin for six over long-off.
He added back-to-back boundaries off Ishant Sharma before the drinks break, worrying India captain Virat Kohli enough for him to waste the first of three unsuccessful reviews appealing for lbw off the glove.
With the ball turning and bouncing awkwardly to the left-hander, Stokes was put under pressure. Attempting to hit his way out of trouble he was reprieved on 31 and 32, Ashwin putting down a tough return catch one-handed and Cheteshwar Pujara failing to pluck a half-chance out of the air at mid-wicket.
Stokes' next attempt at slog-sweeping Shahbaz Nadeem sailed clean for six and when the left-armer tried to regain control, he had the audacity to reverse sweep successive deliveries out of the footmarks for four.
India spurned a run-out chance when Stokes hurried Root through for a misjudged single but with boundaries continuing to flow from the all-rounder's bat and further signs of uneven bounce at both ends, the game was falling into place for England.
Stokes hit his third six of the day at the start of the afternoon session, pounding Nadeem back over his head as Root continued allowing his partner to set the pace.
His eagerness to assert dominance eventually cost him as a slog-sweep against Nadeem took the top edge and sailed to Pujara in the deep. Indian hearts were in their mouths when the fielder juggled the chance, but he eventually smothered the ball.
Ollie Pope, back after surgery on a dislocated shoulder, eased his nerves with an early four but Root was now ready to assert himself again. One flat blow down the ground almost took the non-striker's head off and a reverse lap off Washington Sundar showed off his creative side.
With regular singles keeping things moving, Root picked his moment to go for a rare display of power hitting.
Committing fully to a big swing at Ashwin, the skipper timed the ball perfectly and sent it careering over the boards at long-on for six. For the fifth time in Tests, he removed his helmet and celebrated reaching 200.