The publication of Alan Johnson's second volume of memoirs is timely: Labour is currently in the grip of AJ fever. At both the top and the grassroots of the party, influential figures want him installed as what my former colleague at the New Statesman Rafael Behr calls "shadow secretary of state for working-class authenticity and having lived a bit". Unfortunately, their love is so far unrequited: Johnson shows no desire to return to frontline politics, having quit after four unhappy months as shadow chancellor in 2011, citing "personal issues". Since stepping down, he has carved out a successful media career, which includes sharing a tiny sofa with Michael Portillo on This Week and publishing an award-winning memoir of his childhood, This Boy.
Please, Mister Postman is the sequel, covering Johnson's life from the start of his first marriage, aged 18, to its end in his mid-30s. These are the years during which he left the slums of west London and moved to a council house on the Britwell estate in Slough, where he worked for the Post Office and, later, its trade union.
Readers of the first book might find the slow pace of the second jarring at first. This Boy revealed that Johnson had crammed in an enormous amount of living before he had even reached adulthood. By 18, he was effectively orphaned: his father Steve had deserted his mother Lily (in favour of Vera, the barmaid at the Lads of the Village) before he was in his teens, and his mother died of a heart condition without ever having another serious relationship. At 17, Johnson met his first wife Judy, who was already a single mother, and, before he turned 20, the couple had married and had two children of their own. No wonder he had to renounce his dreams of rock stardom in favour of all the overtime he could manage at the Post Office.
Johnson's next decade was far less turbulent: although the newlyweds were warned on arriving in Slough that the Britwell estate was dangerous, it turned out to be a haven; a tightknit circle of houses around a village green. It also gave Alan and Judy their own front door – something his mother had longed for all her life.
The attraction of This Boy for left-wing readers was obvious: it showed the quiet horror of life before the NHS and the creation of the welfare state's safety net. When Lily died, her son found out that she had worn false teeth for decades – she had seized on the introduction of free dental care to replace her own teeth, rotted and stunted by malnutrition, with far superior falsies. Similarly, the young Alan and his sister received no family allowance (or its successor, child benefit), and his mother was forced to work long hours as a cleaner despite the deterioration of her heart valves. They were lucky to have a council flat – dank, cramped and insecure as it was – or they would have been homeless, too.
This Boy showed that there was at least one "big beast" left in the Labour party who could talk about the struggles of life on the breadline in practical, rather than theoretical, terms. If he returned to the fray, Johnson would be a huge asset in an election that is bound to focus on the future of the health service (the "Tory privatisation agenda" was a recurrent theme in the Scottish independence debate) and the viability of the welfare system. Labour's choice over the latter is stark: commit to swingeing cuts in the name of deficit reduction, or make the case that our "bloated benefits bill" is necessary to keep poor children fed and housed, and risk being painted as statist spendthrifts. Who better to make the case for a safety net than someone whose childhood was so blighted by a lack of one?
The suburban peace depicted in Please, Mister Postman cannot hope to compare with these grand themes. Johnson's muscular, unsentimental prose is just as sharp, but the niceties of mail delivery in the Slough and Burnham area, or knife-edge votes in the executive elections at the Union of Communication Workers, provide less fertile ground for a memoir. This is still a charming book, though: Johnson has a gift for pen portraits, and he recreates the atmosphere of union meetings and Sundays at the British Legion with verve. Again, there is a feeling of a world lost in time, although here it is found in the rigid gender divisions of work and home, rather than Dickensian slums. "I'm conscious that this creates a fair impression of Andy Capp, of a bloke with a self-centred social life that left his wife to look after the kids, cook, wash and make a comfortable home," writes Johnson of his weekly visit to the Legion for beer and bingo while his wife made lunch. "And that was pretty much the division of labour back then."
That tone – matter of fact, free from personal defensiveness – is also evident in his writing on race. We hear about the graffiti hoping to "Keep Britwell White", and of the many Asian and black immigrants working in the postal service, but Johnson is not here to talk politics, or at least not in the way that politicians do. He paints the picture, but he prefers to let the reader draw her own conclusions about what it depicts.
He also makes an unshowy case for the trade union movement, even while acknowledging its flaws. In his recollections of participating in industrial action, and, later, fighting to stop wildcat strikes as a UCW rep, there is an inevitable sense of doom as Margaret Thatcher heaves into view, intent on crippling the movement's power. In one telling anecdote, the outgoing head of the union tells his successor to watch out for the pristine white telephone on his desk, which will ring when cabinet ministers and senior civil servants want his opinion on matters of state. In the next 10 years, it rings once: it's a woman trying to get through to Sainsbury's.
Johnson should also be commended for resisting the memoirist's ever-present temptation to turn every minor event into a dramatic foreshadowing. Where he does succumb to hindsight, it works – one day, a colleague named Bill tells him about his delivery route in Littleworth Common, which goes past a stately home called Dorneywood. (Political geeks will remember this as the scene of John Prescott's notorious croquet session when he was deputising for Tony Blair.) Johnson wonders why there is a policeman stationed on its long drive. "'Ah,' said Bill knowingly. 'When there's a copper on duty it means the man himself is here.' My inquiry elicited the information that the 'man himself' was the home secretary and Dorneywood his official residence. I really want to do that job, I thought to myself later. I wasn't thinking of the role of home secretary but of the job of postman to the good folk of Littleworth Common." Nothing more is said, but once again we remember how few men like Johnson have ended up living in places like Dorneywood.
The coming months will be dominated by the question of how politicians can speak for voters when their lives are often so different from the people they represent. According to a 2010 parliamentary report, the number of former manual workers serving as MPs has fallen from 16% in 1979 to just 4% after the last election. The trend is unlikely to be reversed in May next year: a Guardian study found that half of Labour's candidates in marginal seats were political insiders such as former special advisers or thinktank workers. (Don't expect the other parties to help: the Conservatives had only two former manual workers as MPs post-2010; the Liberal Democrats had one.)
In this climate, the desire for Johnson's return to the frontbench is entirely understandable. But it masks a bigger question: is the route that brought him to high office closed for ever? And what have we lost as a result?
• This article was amended on 15 October 2014. An earlier version said "there is an inevitable sense of doom as Margaret Thatcher hoves into view". That should have been heaves into view.
