The latter, for O’Hagan, is more damaging than the former, which maybe isn’t surprising for a writer who likens friendship to “a set of loyalties that turn in the head like old records”, and worries that people no longer go to pubs because they’re too busy shopping online. “In the age of the internet, what exactly is a friend? … Can you swear by someone whose voice you’ve never heard …?”, he asks, not seeming to mind terribly much – strangely, for an author so companionable on the page – that this isn’t really a feature of online life so much as writing itself; Gutenberg, not Zuckerberg.

In these pages, friendship liberates where family constricts. Growing up with three brothers, O’Hagan’s household was a “zone of adversities”, a “palace of stress”, with an unloving father who once had their dog deliberately driven out into the countryside and set loose, never to be seen again. At primary school, respite lay in tooling around wastelands with Mark, a neighbour his own age. “A great friend can summon a new world order, and, best of all, the beginnings perhaps of a new person for you to be, tugged from the constraints of home.” Later, O’Hagan revises the formula to call another friend’s fellowship “a passport to being the kind of person you wanted to be”.

Metaphors of migration and rebirth feel potent in a book suffused with implicit wonder at the distance O’Hagan has travelled since boyhood. On one page, he’s stacking shelves as a teenager at his local Tesco in Ayrshire; on another, he’s at a party for a new girlfriend at “the Donna Karan store on Park Avenue”. He makes no bones about being an inveterate name-dropper – clubbing with the Stone Roses, whisky with Christopher Hitchens.

But while a lot of life happens in these pages, it’s no tell-all. O’Hagan knows that friendship is rarely just a bowl of cherries, yet he’s discreet, even coy, about the subject’s shadow side: snubs, misunderstandings, fallings-out (“I know a famous actor who wanted me at his wedding, but he didn’t even reply when I invited him to mine”). The level of access, of disclosure, only goes so far: while there’s a brief mention of his aborted attempt to ghostwrite Julian Assange’s memoir (the WikiLeaks founder struggled “to befriend himself”, says O’Hagan, diplomatically), there’s nothing about his lengthy reported piece for the LRB on the Grenfell Tower fire, interesting in this context if only because the ensuing furore must have reminded him who his friends were.

Partly for these reasons, the most intriguing item here concerns the late Irish novelist Edna O’Brien, whom he first met in London in 2009 after leaving Seamus Heaney’s 70th birthday party. When he invites her to lunch at the Wolseley in Mayfair (“Perfect … ask for the corner table, Lucian Freud’s table”), it’s the beginning of a 15-year friendship during which “we called upon each other to complete thoughts we were unable to have alone”, in O’Hagan’s curious phrase, glancingly elaborated on when he later recalls “the soft sonatas we used to listen to while I helped Edna with her manuscripts”.

Of the various names dropped in these pages, she’s the only one permitted an insight into O’Hagan himself. In most of his anecdotes, he’s the guy who comes out best – whether as a schoolboy weeping over Charlotte’s Web when cruder classmates laughed, or as a hardy reveller who is nevertheless earliest to rise the morning after a big night out – so your ears prick up a little when, apropos of nothing, O’Brien tells O’Hagan (observed, for once, rather than observing) that she can see he’s “a wounded man who handles it very impeccably and very plausibly”.

For a memoir – which is what On Friendship is, however piecemeal – that would seem to leave money on the table, to say the least. Ultimately, these memories and musings – in appealingly slimline hardback, eminently gift-ready – leave you wondering about the larger autobiography O’Hagan might write, if and when he chooses.