The 33-year-old, England's record run-scorer, had been pondering the move for most of the year and eventually made the decision ahead of last week's fourth Test with India at Southampton, where his country secured a series win
Alastair Cook had considered retiring from England duty for the last six months before finally announcing the end of his international career.
Cook revealed on Monday that he will step away from the England stage following the fifth Test against India at The Oval this week.
The 33-year-old, England's record run-scorer, had been pondering the move for most of the year and eventually made the decision ahead of last week's fourth Test with India at Southampton, where his country secured a series win.
#ENGvIND— Cricbuzz (@cricbuzz) September 6, 2018
"One of my friends rang me to check I was still alive because everyone was talking as if I'd died! It's been surreal" - Cook opens up about all the retirement chatter.https://t.co/b0tu2s0x9e pic.twitter.com/p6xzfSZbyy
"It's hard to put it into words but over the last six months there have been signs in my mind this was going to happen," former England captain Cook told reporters at The Oval on Wednesday.
"I always had been mentally tough and had that edge to everything I've done and that edge had kind of gone."
Cook informed captain Joe Root before the game and head coach Trevor Bayliss while it was going on, but the rest of the squad found out in a beer-fuelled emotional speech afterwards.
"I told Rooty before the game and then told Trevor during the game," Cook said.
"I was a couple of beers in, which I needed to be, otherwise I would have cried more than I actually did. I managed to hold it together.
"At the end of the game I said, 'It might be good news, it might be sad for some, it might be happy for others but it's time and I have done my bit. I will play one more game'.
"There was a little bit of silence, then Mo (Ali) said something, everybody laughed and then it was forgotten about."
Cook will leave the game as the country's most decorated player, having maximised his talent to its fullest.
"Over the last six months, there have been signs in my mind that this was going to happen." 🤔💭— Sky Sports Cricket (@SkyCricket) September 5, 2018
Alastair Cook outlines why he announced his retirement before the final Test against India and how long the decision has been on his mind. 🏏
Full story: https://t.co/zZmett5Y3k pic.twitter.com/TyxUNJ9RZD
"I can look back and say, I became the best I could become, that actually means quite a lot to me," he said.
"I have never been the most talented cricketer, I don't pretend I was, but I definitely think I got everything out of my ability.
"Everyone was talking as if I'd died. It's nice when you hear so many nice words said about you. The last couple of days I have been back at home but I had a look last night.
"Hopefully this week can go well, score some runs and then I can go."
- 'Real tough cookie' -
India coach Ravi Shastri paid a generous tribute to Cook, saying: "I saw his first Test match, saw him getting a hundred in Nagpur (in 2006).
"He's been one of England's greatest cricketers -- no question. He always came across a mentally tough bloke, real tough cookie. As far as I am concerned, there were times in his career when he batted where he did look the master chef."
Former India all-rounder Shastri added: "He might not go down as one of the best-looking, fluent batsmen, but my word he was effective.
"Playing in these conditions for that length of time, where the ball does move and it's a challenge for an opening batsman -- I think he's been simply outstanding. Good luck to him."
Cook has been given an extra incentive to go out with a century after rock legend Mick Jagger offered a charity reward.
There will be an added bonus for runs scored by England and India thanks to Jagger, who is to donate £20,000 to the Chance to Shine charity for any individual century in the fifth Test.
The bowlers are not being left out on either side, with the same amount on offer for a five-wicket haul.
If one of them manages a three wickets or any other batsman hits a half-century, that will be worth £10,000 for the charity, who provide opportunities for young people to play and follow cricket through involvement in state schools and deprived areas.
Rolling Stones frontman Jagger said: "I follow England - the game in general, in fact - from wherever I am in the world and thought this would be a fun way to make some money for Chance to Shine."