An important collection of previously unpublished letters written by members of the elite Bloomsbury group are set to fetch up to £80,000, auctioneers revealed today.

The material includes more than 700 letters between Helen Anrep and other members of the Bloomsbury circle, including Vanessa Bell, her sister Virginia Woolf and Roger Fry.

Although not an artist or intellectual, Anrep, who died in 1965, was deeply interested in the arts and became a close friend and confidante of many of the group.

They consisted of artists, writers and intellectuals who lived, worked or studied near London's Bloomsbury where they held informal discussions.

Anrep became involved with the circle in the mid-1920s when she met Fry at a party at Bell's studio. She left her husband, the mosaicist Boris Anrep, to be with Fry, and lived with him until his death.

The content of the letters covers a broad range of topics, from family news, recipes and comments on gardening to more emotional and personal issues.

One of the most poignant letters is written by Bell shortly after the death of her son Julian in the Spanish Civil War in 1924, in which she writes: "Helen dearest. In case you hear - Julian died from wounds a few days ago. V."

In separate correspondence, the value of her friendship to other members of the group is summed up in a letter written to her in 1947 by David "Bunny" Garnett.

He wrote: "But Helen, how I should like to talk to you...you must come for more than a night and talking first about our friends, we shall recall the flavour of the past, the atmosphere which made up our lives and which still, by some miracle you have preserved."

The collection of letters date from 1919 to 1947, covering the span of the Bloomsbury era, and will be sold by Gorringes Auctioneers in Lewes, East Sussex, on September 3 with a guide price of between £50,000 to £80,000.

A Gorringes spokesman said today: "Helen Anrep's contribution to the Bloomsbury group in terms of friendship and support is clearly depicted in this collection of correspondence which offers Bloomsbury scholars the opportunity to acquire further insights into the complex web of relationships within the group."