John Lennon’s open letter to his ex-wife Cynthia, written in 1976, has been put up for auction in America.

The letter, dated November 15, 1976 and tipped to sell for £20,000 according to reports by the Daily Express, was originally sent to a US weekly magazine to be printed “without any edits” in reply to allegations Cynthia had made in an article she had published earlier that year in a British women’s magazine.

Lennon rebuffed her claims that his rising LSD use and meeting Yoko Ono had led to the break-up of their marriage, and claimed that Cynthia had visited him in 1974 to ask that they get back together for the sake of their son Julian.

“As you and I well know,” Lennon wrote in the letter, penned after reuniting with Ono after an 18-month separation and when Cynthia had married engineer John Twist, “our marriage was over long before the advent of L.S.D. or Yoko Ono ... and that's reality! Your memory is impaired to say the least. Your version of our first L.S.D. trip is rather vague, and you seem to have forgotten subsequent trips altogether!

“You also seem to have forgotten that only two years ago, while I was separated from Yoko, you suddenly brought Julian to see me in Los Angeles after three years of silence. During this visit, you hardly allowed me to be alone with him for one moment. You even asked me to remarry you and/or give you another child, 'for Julian's sake'! I politely told you no, and that, anyway, I was still in love with Yoko, (which I thought was very 'down to earth').

“There were no detectives sent to Italy. Our mutual friend Alex Mardas went to Bassanini's Hotel to see how you were, as you said you were too ill to come home... Finally, I don't blame you for wanting to get away from your 'Beatle' past. But if you are serious about it, you should try to avoid talking to and posing for magazines and newspapers! We did have some good years, so dwell on them for a change, and, as Dylan says, it was 'A Simple Twist of Fate!'

“Love & good luck to the three of you, from the three of us.”

“As Lennon's official side of the story,” said a spokesman for RR Auctions, “a public he-said, she-said self-defence, these letters represent the unique final chapter in the life of the former Beatle. They are of the utmost rarity and importance.”