Alastair Cook sensed his England team was "stagnating" under his leadership and needed a fresh voice as captain.

As Cook spoke for the first time about his reasons for resigning after an unrivalled 59 matches as Test captain, he was perhaps inevitably required to reflect on the axing of Kevin Pietersen back in February 2014 - an episode he acknowledges put cricket in the spotlight for the wrong reasons.

But much more recent history was the telling backdrop to his own departure.

England's record run-scorer took almost six weeks after England's 4-0 defeat in India to confirm his decision to step aside, but concedes that deep down he knew his time was up once they lost the final Test in Chennai by an innings and 75 runs.

Speaking on Tuesday at Lord's, Cook described Joe Root - the man by far most likely to succeed him - as "a bloody good cricketer" and "an outstanding candidate", but gave honourable mention too to several other contenders for the captaincy.

At The Oval only six months ago, England were within one more win of going top of the International Cricket Council's Test rankings.

They had already endured a patchy 2016, however, and after losing for the first time to Bangladesh and then journeying on without success to India, their eight Test defeats in a calendar year equalled an unwelcome national record.

"We've kind of stagnated if we are being brutally honest," said Cook.

"There is a lot of work to be done and I felt I just didn't have that energy to do it."

Characteristically, he does not dodge the conclusion that he might be part of the problem.

He said: "That's part of the parcel of being captain, you are responsible.

"The dressing-room has been fantastic; the support of the players has been brilliant. It's just, I think, that hearing a new voice could help."

Cook can look back on two Ashes wins on his watch, as well as notable series successes in India in 2012 and then South Africa just last year.

His tenure has, however, been up and down, and he admits the end of Pietersen's international career after England's 2013/14 Ashes whitewash defeat remains a low point.

"I do wish it was done differently," he said.

"Obviously, the decision was what we thought was the best for English cricket."

He does not believe it was the wrong call, just that the issue could have been resolved more sensitively.

"The fall-out was not very good for English cricket," said Cook.

"It was not great to see and be part of it when it was all over the front and back pages and social media.

"The responsibility as a captain and a player is to get cricket in the public for the right reasons ... for that six months it kind of wasn't."

Pietersen's exit divided England supporters and Cook was in the eye of a storm.

He is thankful that his nearest and dearest helped him through.

Cook told Sky Sports: "I felt I was the only person who made the decision. I felt a little bit let down by the ECB in that one period where they let me out to dry a little bit."

He added: "I did bear the brunt of it and my wife saw a lot of it.

"Without her and her family and my family, I would not have lasted as long as I did. That was certainly the toughest moment off the field."

He retained his appetite for the job for almost another three years, but departs knowing he has made the right call.

"The hard bit was giving it away and being honest with myself and going 'yeah, it's time to go', because it is such an amazing job to do," he said.

"Walking out as England captain is very special. Leading those group of men, trying your best for your country and being at the forefront of it is an incredible honour."

But he believed had run his race, saying: "I felt, unfortunately, that I was done.

"It was sad - it's a job you need 100 per cent commitment to. But looking in the mirror at the end of India, I felt I couldn't do that. It might have been 95 per cent, but that's not good enough.

"It's not a job you hang on to like that ... I just felt the team just needed a push in a different direction."

He kept his new year date for a tour debrief with England and Wales Cricket Board director Andrew Strauss, but for Cook it was already a foregone conclusion that someone else will be leading the Test team out at Lord's against South Africa in July.

"I think getting on that plane, leaving India, if I was brutally honest, I would have been very surprised if I captained (England) again," he said.

"I didn't want it to be an emotive decision. From what happened in those two tours of Bangladesh and India and a bit of personal stuff as well, being away for a long time from a young family - I didn't want that to cloud my decision.

"But it was quite clear when I got home, those thoughts didn't change.

"You could have had those six months when you're sitting there and the pressure's off, you are not playing cricket, you can kid yourself a bit, but unfortunately I wasn't for kidding.

"I've been to the well a couple of times as England captain and I couldn't go again unfortunately."