One thing they do share is the same biographer. Andrew Motion won the Whitbread Prize for his life of Larkin in 1993, and his Keats is published today. A careful scouring yields unexpected common ground. Larkin's view on what your mum and dad do to you more or less holds good for Keats, whose parents both died young. Neither poet married, sharing the view that you can't satisfy both spouse and muse. Each left behind a helpful mountain of correspondence. And both had immensely touching death scenes. "Thank God it has come" were Keats's last febrile words to his companion Joseph Severn. Compare and contrast with Larkin's doomy whisper to his nurse: "I am going to the inevitable."
But then perhaps we'd all get a beautiful demise if we could commission Motion to write it up. His immensely moving description of Keats's final illness in Rome derives an uninvited piquancy from Motion's belief that he, too, was going to the inevitable. About six months from completion, a bunch of pins and needles pitched camp in Motion's legs and wouldn't budge. He chose not to go to a doctor until he had handed in the manuscript, and "thought I'd had it. It's not becoming of me to say it, but of course I had to hope that some of the things that I was thinking about would get into the last pages I wrote."
His neurologist offered him a multiple choice of potential diagnoses: MS, motor neurone disease, or a tumour on his spine. The scan showed a benign tumour which was duly removed, so here Motion is, back in the study in Keats House in Hampstead where he spent two years rifling through the tomes that line the wall. He is now working out how to keep his side of the deal in all the plea-bargaining he did with a God in whom he doesn't actually believe. To help with one promise - simply to put his feet up - he followed Keats's example.
"As soon as I'd clocked Keats's thing about `diligent indolence', I thought yes, I can justify this to myself." Other clauses are proving tougher. "I said things like `If you let me off, I'll enjoy your beautiful creation more. Be nicer to people.' " And? "Fat. Chance."
It's hard to imagine Motion requiring the threat of death to implement either of these. He is, in the least pejorative sense, an aesthete, and a famously charming one too. Both these attributes are at one with his appearance: he has Larkin's height and Keats's pulchritude (rather than - worst scenario - the other way round), and the softest of honeyed voices.
So Motion's biography has been postponed. Here's the outline, though, which a future biographer will easily be able to flesh out from the stockpile of six letters he very unfashionably writes a day. An unlatinised version of the curious surname came over with the Vikings. "There is a village in Norway called Moshen. They went to Scotland for a bit of rape and pillage, I suppose, and then gave that up and took up baking. There is a gravestone up there with `Andrew Motion' written on it. I have a photograph of it which I quite often take out and look at." He was brought up "on the Essex- Sussex border" and went to boarding school, which he loathed until embarking on A-level English. "One of the first poems we read was `The Eve of St Agnes'. It really was like somebody turning the lights on."
With the lights turned on, Motion formulated two ambitions: to become a poet, and write a biography of Keats. One of them took no time, the other a quarter-century. His first poem was published when he was 20, his first collection when he was 25. By then he was teaching undergraduates at Hull, where he fell in with the university librarian. Larkin paid him the inestimable compliment of offering to buy an early manuscript for the library. "He said, `Before you say yes I think I should warn you that I once sold one of mine and I am still feeling for it like a missing tooth.' I said, `My teeth are all right.' But I quickly discovered exactly what he meant." An almost complete set of teeth is therefore stacked away at home in Tufnell Park.
Motion has a metronomic output of about 10 poems a year, of which he keeps six. His latest is "Mythology", an elegy to Diana, which thoughtfully develops Spencer's image of the huntress hunted. "Besides the river / Swerving under ground / Your future tracked you / Snapping at your heels..." It's another of his melodious send-offs, and solid proto-laureate stuff. He already does people's poet duties like critiquing the latest Oasis lyrics for the Today programme, but he's quick to stamp on the idea that he'll eventually fill Ted Hughes's boots. "I think it should be Wendy [Cope]," he says, although he adds that "I think that poets ought, like carpenters, to be able to build something when they're required to."
Which brings us round to Keats. Three perfectly good biographies were written in the 1960s, of which Robert Gittings's has lasted the best. However, if you put the indexes end to end, the word Napoleon barely appears. So clearly there is something to be done by way of putting him into context, let alone exploring how he reacts to the context." In Byron's famous snub, Keats was "always frigging his imagination", and that is the image that has come down, abetted by Severn's suffocatingly idealised posthumous portrait. Motion's contention is that Keats engaged kinetically with the world around him. He talked politics, caught the clap from prostitutes, and (unlike Larkin with his naughty magazines) "said yes to life".
Whatever the differences between the two poets, Motion's two biographies themselves differ importantly. Where Keats is interpretive rather than revelatory, his Larkin is what he calls an "I-was-there type biography". As Larkin's literary executor, Motion was instrumental in preserving all papers apart from the steamy diaries, which a loyal retainer shredded. "If they had been given to me I would have done what Sir Bedivere does and hoped I'd have got away with it."
And what of Motion's papers? Does the unreliable destroyer have plans to mince his own private musings? "I think it would be very vain. Much vainer than to keep them. That's my line anyway." He then admits that six years ago some papers did find their way into the bin, and adds that he finds the subject "extremely embarrassing to deal with for some reason". There is an entire book called Keats and Embarrassment. Perhaps the eventual biography ought to be called "Motion and Embarrassment". `Keats' by Andrew Motion is published by Faber & Faber at pounds 20;
`Salt Water' was published earlier this year by Faber and Faber.