Tea India 582 for 5 (Nair 195*, Ashwin 54*) lead England 477 by 105 runs
Live scorecard and ball-by-ball details
Karun Nair entered the 190s as India stretched their lead past 100 with four sessions remaining in the Chennai Test. Nair went to tea batting on 195, and will have to endure 20 more nervy minutes before resuming his bid to go past his Karnataka team-mate KL Rahul, who was out for 199 on day three. Nair and R Ashwin added an unbroken 147 for the sixth wicket and upped India's scoring rate in the second session, scoring 119 runs at 3.97 per over, as England's bowling wilted after a disciplined performance in the first session.
Nair scored 75 in the post-lunch session, at a strike rate of 87.21. He was severe against the spinners, punishing anything short and managing to find the leg-side boundary frequently with his sweeps despite the almost constant presence of deep midwicket and deep backward square leg. There were also some excellent shots against seam, including a ramp over the keeper when Jake Ball bounced him and an orthodox square-drive when he pitched it up.
Nair could have been out on 154 when he tried to reverse-sweep Adil Rashid and sent the ball into Jonny Bairstow's gloves - replays and Ultra Edge suggested it had deflected off the face of his bat. The umpire said not out, and England had no reviews left.
Ashwin, who was batting on 9 off 36 balls at lunch, also opened out, signalling this change of approach by stepping out and swinging Moeen Ali over the long-on boundary to move India into the lead. During the course of his innings, he became the first batsman since 1985 to complete the double of 25 wickets and 250 runs in a Test series.
As tea approached, Keaton Jennings' occasional medium-pace looked the likeliest source of a wicket, sharp reverse-swing nailing R Ashwin's pads and gaining the umpire's approval, only for ball-tracking to show the ball was heading down the leg side when the batsman reviewed.
England took only one wicket in the first two sessions, Liam Dawson picking up his first in Tests with an arm ball that hurried into M Vijay to hit him on the back pad in front of middle stump. Vijay consulted with Nair and reviewed, perhaps unwisely, because this was the definition of plumb. Earlier in the morning he had stood his ground when umpire Simon Fry had failed to spot a thin edge off Stuart Broad, perhaps aware that England had no reviews left.
Vijay saw Nair through a nervy period in the nineties, exhorting him from the other end to stay calm and wait for the scoring opportunity. Having played out five dots from Ben Stokes on 99, Nair reached the landmark by defying a packed off-side field, which included two short covers for the uppish drive, stretching out to a full, wide ball and letting it come to him to steer it past the diving backward point fielder.
That was only the third boundary Nair hit in the day in 49 balls, the others an unintentional four while trying to leave Broad and a nimble skip down the pitch to loft Dawson for six over long-on. It reflected the hard-nosed approach India had had to take in a session where England set defensive fields, bowled with discipline, and extracted more help from the pitch than they had on day three.
Inconsistent bounce was far more frequent. Dawson beat Vijay's outside edge with turn and jump in the second over of the morning, and three balls later nearly bowled him with one that crept low. Stokes, hitting the pitch hard, often got the ball to lift as lunch approached, taking a chunk off the shoulder of Nair's bat and hitting Ashwin's glove - on the index finger of his bowling hand.
As if to balance out the impact of the uneven bounce, the pitch seemed to have slowed down a little more too. Ashwin, who likes the ball coming on to the bat, had to twice abort attempted back-foot punches off Dawson because the ball stuck on the pitch. By lunch, he had ground out 9 off 36 balls.
Added to these factors was Alastair Cook's captaincy: he bowled the accurate Dawson unchanged from one end - he sent down 13 overs for 31 runs - and his seamers from the other, only using Adil Rashid for one over - the last one before lunch - and not using Moeen at all.
Rashid's introduction brought a little spike of aggression from Nair, who made himself a bit of room and drove him inside-out to the cover boundary. It was just a teaser of what was to come after lunch.