Karun Nair almost never made his Test debut. In July 2016, while on a pilgrimage trip in Kerala to give thanks for his ODI debut, a boat he was in capsized. Six people drowned.

Four months later, Nair was in India's squad to play five Tests at home against England. He made his debut in the third Test, in Mohali, as an injury replacement for his childhood friend KL Rahul.

"It was the first time I was picked in the main squad. It was a day or two before that Anil sir [Kumble, then head coach] and Virat [Kohli] spoke to me, and that's when I knew I'd be playing," Nair remembers.

Forty-one of his 47 first-class innings had come inside the top five until then, but Nair started at No. 6 in his first Test for India. He run out for 4. In the next Test, in Mumbai, he was out lbw to Moeen Ali for 13.

Heading to Chennai for the final Test, Nair's mind was full of thoughts of whether he would be picked again. The city itself was preoccupied with dealing with the aftermath of cyclone Vardah. Large parts of Chennai had been inundated with rain and obstructed by fallen trees. For the two teams, the immediate fallout was that no practice was possible ahead of the match.

"Not to have any practice session because of the cyclone, which no one could control, [hurt]," Nair says. "We were just in the hotel. [That gave me] a lot of time to think about what to do and what is going to happen. [It was] on the day of the match that we got to head to the nets and have a knock."

It was Chennai's first Test in three years, and former BCCI south zone curator PR Viswanathan and his team were determined to get it underway without any delay.

"The only issue was a slightly higher level of surface moisture in the pitch," Viswanathan says. "So after the cyclone, we dried the surface with charcoal. We rolled charcoal with the stumps so that the heat doesn't directly come in touch with the pitch and the grass.

Nair had extra motivation to do well in the match, given his parents were watching from the stands. "My dad didn't travel outside Bangalore to watch my games, so when I made my debut, Anil sir told me, 'You should call your dad here', but I didn't. So for Chennai, he himself called my dad, who came along with my mom. She came for the first time, so that was really special of Anil sir."

England captain Alastair Cook chose to bat and a century from Ali and fifties by Joe Root and the lower order took them to 477.

Cook's opening partner, Keaton Jennings, who made 54 in the second innings, remembers that despite being 0-3 down in the series, the team wasn't beaten down.

"The guys were pumped up," Jennings says. "It was seriously hot, [but] we were keen to try and give it one last push and leave with a win."

England's long first innings turned out to be a blessing in disguise for an out-of-touch Nair.

"We fielded for two long days. In those two days, I managed to get some batting practice after the day's play and made sure I hit the nets with Sanjay Bangar - our batting coach at the time - so that I was feeling more comfortable when my chance to bat would come.

"And when I went in to bat, it was a kind of a tight situation. After a point, I let go of my personal situation and only started thinking about what I should do for the team to get us through that situation."

When Nair walked in, India were 211 for 3, having lost Cheteshwar Pujara and Virat Kohli in quick succession. England's fast bowlers were moving the ball around and there was turn for the spinners. Nair nicked one from leggie Adil Rashid past slip and was scratching around for his runs - getting 13 off 42 balls - when his batting partner came up to talk to him.

"The pressure affected how I started," Nair says. "But I was lucky that I had Rahul with me. Having played so much together, to have him was helpful. He made me realise that I need to get out of the shell. It was then I got a couple of boundaries and I felt much more free.

"When we were 11, we were in the Karnataka Under-13 team. Since then, we have played all age groups together. So it was just like batting in another game for Karnataka because it felt so comfortable batting with him."

Nair's nerves settled, but there were still a few close shaves. On 34, he poked at a full delivery outside off from seamer Jake Ball and the ball flew to first slip, where Cook dropped a difficult catch.

"We gave Karun chances, and it is hard work in that Chennai heat," Jennings says of that moment, when England were still 185 ahead.

Paul Farbrace, then England's assistant coach, believes they should have gone harder at Nair.

"When you have a new player in the opposition, you want to test him. But we never built enough pressure on him… The more he [Nair] got in, the better he played. From 80 or 90 onwards, he played exceptionally well. Stuart Broad bowled very well and we got quite frustrated that it just didn't seem to go our way."

Nair and Rahul's 161-run stand was broken when Rahul fell to a tame shot on 199. Nair was on 69 then and looked set to get a big score. In fact, he achieved what only two other Indians before him had done - converting his maiden Test hundred into a double. "Once you get comfortable with the match situation, everything becomes easy and also opens up to a lot of different possibilities," Nair says. "You have to just grind yourself out of the tough times."

England kept looking for answers with the ball, and Jennings reveals they even tried chat in an attempt to dislodge Nair.

"Initially we were trying to put him under pressure through words [but] when somebody gets to 200, you've got to try and get them out rather than just talking."

Nair doesn't remember any chatter from the fielders. "They were very tired, so there was no chat - or maybe I didn't hear even if there was any. I think they were waiting for us to declare!"

England got another chance when Nair was on 217 - a nick off Ball again, this time dropped by Root at slip.

"I think there would have been a bit of fatigue and frustration crept in [by the time of the Chennai Test]," Farbrace says. "That's definitely the case, but at no stage did we think, 'It's the last game, [we] just want to go home now.'"

As Nair closed in on a triple-hundred, time was running out. With a hefty lead in the bank, a declaration was looming.

"There was a message when I was at about 220: 'We have about six to eight overs to play. Try and score as many as you can.'"

Jonny Bairstow missed a stumping when Nair was on 246, and in the four overs after he passed 250, he hit six boundaries off Ali and Rashid to race to 294. On 299, he was facing Rashid. The field was up and Nair tried to sweep from off stump but missed, and England erupted in an appeal.

"After playing so many shots, I was confident of putting away another sweep," Nair says of playing against the turn. "And I was confident of it being not out because Rashid was bowling more outside off."

Farbrace had been hoping for exactly the opposite. "I was thinking, 'Please just give him out!' Otherwise it could be another hour and he would still be batting. He was just completely controlling the innings."

Rashid had four men close on the off side for any potential chance offered. On the ball after the appeal, he pitched one short and wide, and Nair went for the cut. Cook, at extra cover, dived forward to catch but it landed short and went past him to the boundary.

Nair became only the second Indian to a Test triple-century, and the third batsman overall to convert his maiden Test hundred into a triple.

"It was surreal," he remembers. "It was such a special feeling. I didn't realise that [at the time] because I was very tired. I had never thought about me being there."

"It was an innings of a lifetime," Farbrace says.

India declared right after, on a record 759 and wrapped up an innings win the next evening to take the series 4-0.

"The declaration was pushed for another over or two till I got my 300," Nair says. "Those were special moments and something that I can look back upon. I credit my parents for supporting me throughout my career and all the coaches who have helped me to get to the level that I have. It's a combination of hard work, determination and talent for me to get to where I got."

Himanshu Agrawal is a sub-editor at ESPNcricinfo