A major archive of letters and photographs sent between Marcel Proust and his male lovers is to cross the block at Sotheby's Paris on May 31.

The collection also includes letters to family members and manuscripts of his work.

Marcel Proust (seated) with his lover Lucien Daudet (right)

It's expected to make around $850,000.

Proust was gay at a time when being so was considered unacceptable.

He worked hard to keep his orientation hidden, even fighting a duel against a man who questioned the nature of his relationship with the writer Lucien Daudet.

Benoit Putteman of Sotheby's told the Telegraph: "These photos are the originals that Proust kept at home and that he asked his friends to send him.

"They are very touching as it was his way of keeping close to his loved ones."

The letters include a number written to the composer Reynoldo Hahn, with whom he had a tempestuous affair.

He writes in one candid letter after they broke up: "I think only that while I love you a lot less, you no longer love me at all…

"I won't let you commit such stupid, such cruel and such cowardly acts without trying to awaken your conscience."

Proust is considered one of the most important authors of all time and memorabilia associated with him commands a premium.

A copy of his debut novel, Swann's Way, dedicated to his lover Lucien Daudet, sold for $821,627 at Sotheby's Paris in 2014.

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