The man who could have been prime minister seems to have come to terms with the quieter life. He says, "Never say never," when asked if he could return to the Shadow Cabinet. "But I'm doing other things now."
Alan Johnson is writing a book. "It's about my first 18 years – up to the rock'n'roll years," he says. About his mother, who died when he was 12, and his sister, who looked after him. His is a remarkable life – "I didn't do it to get a back story" – from orphan, to mod, to postman, to union leader and then cabinet minister.
He hasn't read Alistair Darling's memoir. "I've read some great stuff – The Moor's Last Sigh. I've read Vanity Fair, which I started when I was 18. I got it out of Ladbroke Grove library, and then we got shifted to Slough, to a council house. I went all the way back to return it, but it was a long, hot summer and I was doing 12-hour days at the Post Office, so I never finished it. Just such a delight. I always used to do some reading when I was a minister, but there were some books where you thought, that requires a couple of weeks' serious reading, and you're not going to do that with ministerial boxes."
Two red boxes sit in front of the fireplace of his comfortable corner office over the road from the House of Commons, a reminder of authority, and homework, past.
"I don't rush to read political memoirs. I never really have. I mean, I'm reading Tony's A Journey and I'm up to about page 300. It's there when I don't fancy reading fiction. So, no, I haven't read Alistair's. I've read the extracts. Given that he was so close to Gordon and then was estranged and they tried to get rid of him, you can understand a desire to put the record straight. That didn't happen to me. I didn't have that kind of shenanigans."
He says the party has "largely" got over the division between Blairites and Brownites. Ed Miliband "bent over backwards" to appoint Blairites such as him to top Shadow Cabinet posts – and "you can't blame Ed" for their absence now. He won't talk about his private life, but plainly the collapse of his marriage in January, which forced his resignation as Shadow Chancellor, had nothing to do with Labour's civil war. But when I ask if there is still a tension over policy on the deficit, his answer is telling: "What we needed to do, and what Ed Balls has done – his mea culpa last week about banking reform was absolutely the right thing to do – in order to criticise what has been a disastrous economic policy ... we had to say where we got things wrong. And one aspect was banking regulation." (Balls had told the Commons the previous week: "For the part that I and the last Labour government played in the global regulatory failure, I am deeply sorry.")
I ask whether the British public will ever take to Balls: "That might be an issue about the leader. I don't think it's an issue about the chancellor of the Exchequer. The public expect the chancellor to be a bit of a bastard. He's got to say no to a lot of people, and you've got to be pretty tough to do the job."
It is an issue about the leader, though. A recent poll found that half of Labour voters could not imagine Ed Miliband as prime minister. "Look, we're judging him on his first year, having taken over the most difficult job in politics at the most difficult time in the most difficult circumstances. How's he done at the end of the year? The comparison isn't with Tony Blair and it isn't with David Cameron, whose parties had lost four and three elections respectively when they took over. The comparison is with Thatcher, with Hague, with Foot." Hague and Foot? Hmm.
But he is impressed, he says, by the plan to allow supporters of the party a say in choosing the leader, to dilute trade union votes. "He is going to tackle our dreadful system of electing our leader."
He admits that former long-serving cabinet ministers such as he and David Blunkett are a problem for the leader, because they didn't like it, for example, when Miliband said ID cards were a mistake. But he says that is Miliband's "'civil liberties' issue", as if the Labour leader is allowed a symbol. He says Miliband is "fine" on the DNA database, CCTV and police numbers: "And he was fine on control orders, in the end, when it was all explained to him." Johnson, a former home secretary, says that control orders are "back in another language", but he is surprised that Cameron has allowed them to be "weakened".
Liberated from front-bench responsibility, Johnson is also free to drop any pretence that he agrees with the leader on scrapping tuition fees and replacing them with a graduate tax. He regards their introduction in 2003, which he steered through the Commons, as one of the high points of his career. Indeed, he claims that "everyone says" tuition fees are "right" – the only argument is over their level. If Labour were still in government, he says they would have been capped not at £9,000 a year but at "something like" £4,000 or £5,000.
He says Ed Balls, his successor as Shadow Chancellor, is "doing well", but it does not stop him commenting on the economy. Unlike Jim Murphy, the shadow Defence Secretary, who said last week that the euro cannot survive in its current form, Johnson says it must. "If the whole thing goes belly up, particularly at this time in our economic fortunes, that has huge consequences."
He does not accept that Ed Miliband's instincts are to abandon the centre ground and move the party to the left. "We moved the centre ground to the left," he says, and the economic crisis has moved it further. "If we were still there and TB were still leading us, we wouldn't be saying that we were comfortable with the filthy rich."
And he has one final piece of advice for the young leader. Coalition government. "We had all better get used to it. It shouldn't hold any fears. There's nothing wrong with coalition. I think the Lib Dems actually did the right thing in the way that they talked to the Tories first, talked to us, didn't work out, did the deal – I wouldn't criticise any of that. And I wouldn't criticise them for being in coalition. I criticise the things they have done in coalition, particularly on student fees and the economy. They've made big mistakes there, but the act of being in coalition itself – it's doubtful whether the British public will give a majority to any one party in future. We may well be in coalition territory for a long time. So, yeah, coalition with the Lib Dems. Coalition with the Tories? Never."
Read more of the interview at: independent.co.uk/jrentoul