Lennon letter on Beatles' breakup to be auctioned

A private letter written by John Lennon to Paul McCartney, due to be auctioned in the autumn, confirms the anger and bitterness festering within the songwriting partnership before the break-up of The Beatles in 1970.

In the six-page hand written letter, written at the nadir of relations between the Fab Four, Lennon criticises the effect fame has had on McCartney and compares his wife, Linda, to a "middle-aged, cranky fan".

It is unclear what happened to the emotional letter, which swings from tirade to affection, after it left Lennon's possession or whether the draft was ever sent.

Lennon wrote the undated letter, which is littered with spelling mistakes and expletives, at his Berkshire mansion, Tittenhurst Park, around the time when the band's company, Apple, was breaking up and its members were suing each other. Lennon appears to think the unprecedented adulation had gone to McCartney's head. "Do you really think most of today's art came about because of the Beatles?" he asks. "I don't believe you're that insane. Didn't we always say we were part of the movement, not all of it? Get off your gold disc and fly."

The letter also confirms that the Beatles had, in effect, split up months before the official announcement. Lennon criticises – and swears at McCartney for – the pressure the other members put on him to keep quiet.

However, his anger pours out in defence of his relationship with Yoko Ono. He is also scathing of the McCartneys' relationship. Linda, he says, had "a petty little perversion of a mind", but he later signs off with some affection: "In spite of it all, love to you both from us two."

The letter is being sold at Christie's by an anonymous vendor who bought it in an auction in the early 1990s. It is expected to fetch at least £70,000.

* Sylvia Plath, the late wife of Ted Hughes, committed suicide by putting her head in a gas oven after reacting badly to drugs she took by mistake, the former poet laureate claims in a letter recently acquired by the British Library.

Plath, a feminist poet, had had problems with the unnamed drug before when living in America, but had been prescribed it in Britain in 1963 under a different brand name, Hughes says in the handwritten 1981 note to his biographer and confidante, Keith Sagar.