Here's an excerpt from Harry Thompson's biography of Peter Cook, concerning Cook and John Lennon during the sixties:
[Peter's] basement kitchen became the setting for a series of huge dinner parties, hosted by [Peter's wife] Wendy with almost military precision. As often as three times a week, every week, up to twenty guests would gather round the big dining table, which literally creaked under the weight of ratatouilles, moussakas and quiches lorraines. Peter, a self-confessedly awful cook, would take no part in the preparation of the feast; instead he would sit and hold court at one end of the table, ensconced in a large Windsor chair. Wendy would sit at the opposite end, on a slightly smaller seat. Lined up between them on either side of the table were London's famous, celebrities of all shapes and sizes assembled in a deliberately eclectic mix. Regular guests included John Lennon, Paul McCartney, Charlotte Rampling, Peter Sellers, Cat Stevens, Peter Ustinov, Ken Tynan, John Cleese, Paul Jones, John Bird, Eleanor Bron, Willie Rushton, Michael Foot, Bernard Levin, Jay and Fran Landesman, Malcolm Muggeridge, Victor Lownes, and of course Dudley and Suzy Kendall. Most of the guests were purposely selected for their fame and interest value, but they were almost all distinguished by the fact that they had sought Peter's friendship, rather than he theirs. As Barry Fantoni points out, 'Peter was the sixties icon. Pop stars were presented to him at parties, not the other way round.'
Harriet Garland remembers 'Wonderful, happy, happy evenings at Church Row, with John and Cynthia Lennon and Paul McCartney. Lennon was there a great deal. Wendy would do this wonderful spread -- she was very ambitious -- she'd think nothing of roasting a whole boar for instance, and putting it on the table; and it was all wonderfully decorated, with fantastic puddings. I've never laughed so much in my whole life -- Peter and Lennon were just frightfully funny together. The two of them would do an act: Peter was always becoming somebody, Barry McKenzie or E.L. Wisty or whoever.' John Lennon, in fact, told Peter and Wendy that he had written the song 'Lucy in the Sky with Diamonds' for their daughter.
[I'm skipping a few paragraphs here.]
Jonathan Miller's comparison between the Fringe quartet and the Beatles still held true to some extent: Peter and John Lennon had become drawn to each other because of their profound similarities, both being sharp, cynical, witty and the brains of their respective writing partnerships. Dudley and Paul McCartney were in each case the housewives' choice of the duo, their wholesome, sympathetic, and in some ways greater mainstream appeal providing a slight source of irritation for their more caustic and dominant partners. In each case, however, the relationship was symbiotic; both Peter and John Lennon knew, deep down, that they performed better with their sidekicks than without. It is interesting too that both men, unaccustomed to deferring to others in public, did so in each other's company, giving each other space in which to perform. The Cook-Lennon dinner party double act gave Lennon more room than Peter ever afforded Dudley. A further similarity, of course, was that by the mid-1960s both Peter and John Lennon's marriages were, though they were unaware of it, on course for disaster.