John Lennon called Linda McCartney "cranky" and "middle-aged" in an emotional letter written to her and husband Paul that will go up for auction in October.

The letter, written around the time of the 1970 breakup of the Beatles, will be auctioned off by Christie's in London on October 4. It's held by an anonymous owner, and the auction house estimates it will fetch up to 80,000 pounds (more than $113,000), according to a Christie's spokesperson.

In the six-page letter, Lennon slams McCartney for the way he and the other Beatles treated him and wife Yoko Ono. "I hope you realize what s--- you and the rest of my kind and unselfish friends laid on Yoko & me since we have been together," Lennon wrote, according to the auction's catalog. "It might have sometimes been a bit more subtle or should I say 'middle class' — but not often."

Apparently written in response to a letter from Linda attacking Lennon for publicly criticizing the Beatles, the letter reveals Lennon's frustrations with the compromises brought about by fame. "I'm not ashamed of the Beatles but of some of the s--- we took to make them so big," he wrote. "I thought we all felt that way in varying degrees — obviously not."

Even though the letter predicts that the McCartneys' marriage won't last ("See you in two years — I reckon you'll be out then"), it ends on a touching note that suggests the depth of the former songwriting partners' feelings for each other. "In spite of it all, love to you both from us two," it concludes.