As one of the 20th century’s finest poets, Philip Larkin is closely studied, both poetically and personally. Andrew Motion’s biography and Larkin’s Selected Letters, both published in the decade following his death in 1985, revealed that not only was he the lonely, lugubrious librarian everyone had always suspected, but also a racist, child-hating misogynist with a penchant for porn.

In 2001, it was announced that a huge new stash of letters by Larkin had been discovered, following the death of his long-term lover and confidante Monica Jones. Some 1,500, along with 500 postcards, were unearthed in the ramshackle house owned by the latterly alcoholic Jones and were sold to the Bodleian Library in Oxford. Curiosity soon swelled in literary circles: would they underline Larkin's already tarnished reputation or reveal a softer, more sympathetic side?

Anthony Thwaite, who Larkin’s joint literary executor with Andrew Motion, was entrusted with sifting through this colossal epistolary mound. “Really these letters are the most intimate form of self-portrait that we have,” says Thwaite, who spent five years distilling them into Letters to Monica, published this week. “The diaries that he kept for years were the one specific thing that he asked Monica to have destroyed. So we’re just left with the letters that he sent to people — but the ones to Monica are of a particular type.”

Though much of Letters to Monica is devoted to fairly banal themes — something Larkin embraced: “He was very fond of the commonplace,” notes Thwaite, who first met Larkin in 1958 — there is wit and literary verve on every page.

Larkin and Jones gained first-class degrees in English from Oxford and later met at University College, Leicester, when they were both 24; he was an assistant librarian and she an English lecturer. Their shared love of literature was integral to their relationship. “It’s absolutely fascinating to see their views on writers,” says Thwaite. “At one stage, Larkin draws up a table comparing Yeats to Hardy, explaining what he hates in Yeats’s poems or what he likes in Hardy’s poems. It is very entertaining. Larkin and Jones clearly shared a lot of tastes, but they didn’t agree about everything. She was very fond of Walter Scott, for example, and he found him unreadable.”

Larkin’s famous gloominess is plain throughout the letters, as is his lack of confidence about his work. His first draft of his much-loved poem The Trees, for instance, is self-reviewed in excoriating fashion: “First verse all right, the rest crap,” he writes of his “16-year-old’s poem about spring etc”. There’s tenderness, also, towards Jones, whom he refers to as ‘Bun’, although also hints of the guilt Larkin felt when he embarked on affairs with other women. “I have felt extremely remorseful and upset and appalled at the situation I have created,” he writes to Jones in April 1964, about his romance with colleague Maeve Brennan. As for his more unpalatable remarks about immigrants, or other bigoted quips, these are largely absent from these letters. Thwaite says that they were mostly contained in his letters to his lifelong friend Kingsley Amis, which were “a kind of performance, a sort of mad tennis match, a duel”. Thwaite insists that Larkin was emblematic of his “politically incorrect” age.

“Reading Larkin’s own poems, you wouldn’t think that Larkin was a man of the left or advanced in his opinions,” says Thwaite. “He is a figure of his time. He speaks in the terms of his time. Some people who read the letters have absolutely no sense of history, of the context. It makes me very irritable that it is so.

“Why it should have been such a revelation reading Larkin’s letters or Motion’s biography when you’ve got the poems? Often commentators whip up this frenzy: god, look how awful this man was. If only they had read his poetry, they could have seen that there were aspects of this in the work already.”

While admitting he finds Larkin poems like Homage to a Government (about British troops fighting abroad) “an extremely unpleasant, right-wing poem” and conceding that there were sides to the man that were “not the most lovely and admirable”, Thwaite maintains that he was a peerless poet who could be highly charming in person.

“Face to face, he was one of the most amusing, agreeable people to be with. My children all remember Philip with great pleasure. Although he went on about loathing children and so on, he was extremely good with children. All this business about ‘remove the babies from my sight’ was just an act. He was full of performances. He was very entertaining.”

* Letters to Monica is published by Faber at £22.50.