“The female oaf is utterly intolerable,” remarked Virginia Woolf in 1938 of young Anastasia (“Baba”) Anrep who, with her brother Igor, also prompted the novelist to declare “their manners non-existent — save when they hurl a club at that soft bear their mother”, Helen Anrep.

As Woolf’s pen could be more wounding than any club, some comments about them were suppressed in her published letters and diaries. With the surfacing, however, of the last substantial Bloomsbury trunkload, Helen Anrep emerges as a much appreciated recipient of vivid, unknown letters, about 700, which relay choice gossip and affecting anecdote from numerous people, including many from Roger Fry, a great haul of Vanessa Bell, some vintage Carrington, witty Augustus John and a concerned, humane Virginia Woolf.

This corner of Bloomsbury’s sex and the city was St Petersburg, where Boris Anrep, born in 1883, was of distinguished ancestry. He abandoned a legal career after finding a Bloomsbury outpost in Paris and took up mosaics. He moved to England, and after having two children with Helen Maitland, he married her in 1918.

Her hopes of stability, after an entanglement with the artist Henry Lamb, were soon dashed when Boris graced their home with a lover. Helen found comfort with that brilliant curator, critic and letter-writer Roger Fry. Twenty years Helen’s senior, Fry had endured his wife’s madness (and incarceration) and after a romance with Vanessa Bell, and a brief one with Josette Coatmellec, who shot herself on the Le Havre cliffs in 1924, a year before he met Helen, with whom he lived until his sudden death at 66.

Virginia Woolf wrote his biography (1940). Its writing had brought closer contact with Helen, to whom Fry wrote numerous letters. Although this new cache reveals some difficulties, it was — as he told Gide — the “domestic happiness which has escaped me all through my past life”.

After Anastasia’s death in her mid-nineties, some papers surfaced, now in the Tate; with Igor’s recent death (despite Virginia’s predictions he became a trusted cardiologist), more have emerged, trunk-burstingly so.

“I’m greatly pleased by all your flattery,” Virginia tells Helen in 1925. “Especially do I like Monk’s House to be flattered — Vanessa never loses a chance of snubbing it. If she says ‘it’s so like you — she adds, ‘so romantic & overgrown, & utterly distasteful to my way of thinking’.”

Their sibling rivalry was a creative force but, in 1940 she concedes of Vanessa’s home at Charleston, where she watched a play and drank cider, that it “seemed very lovely, and the creation of that world in the hollow of disaster a great triumph” and she recalled a similar Cambridge evening: “Rupert Brooke, stealing his father’s cigars, and the nightingale — dear me, how old I’m getting. When one brings in nightingales, then one has lost touch with reality.”

For Carrington a bee was all too real. It “got in my hair and stung me on the top of my head at two o’clock in the garden. I rushed into the house. In three seconds the palms of my hands, the soles of my feet started to itch. I shrieked for Ralph and lay on a sofa. I then nearly fainted, and felt desperately ill. I was then sick for almost five minutes violently. Then diarörahee & sick at the same time, & nearly fainted. Then violent grips in the stomach really for an hour, till Ralph gave me some opium which took it away. And then, even more mysterious the whole of my body rose up in great pink lumps as if it had been flayed with nettles. The torture of this phase was exquisite! This lasted for 2 hours. . . . Poor Ralph was completely broken by the horrible contortions he witnessed.”

That last sentence makes the anecdote, and is a reminder how much they all needed one another as much for support as banter. Charm itself, Augustus John relied upon Helen’s comments about his writing (he took “refuge in an irony which I trust some people will be able to see through”), and reveals that one model, although “undeniably picturesque”, was “too bloody polite for one thing and secondly shows herself to be intellectually incurious!”.

Robert Graves’s daughter tells Helen of an Oxford man “who has become less rampaging without losing spark. Through me. I feel guilty but I think it’s better from a practical point of view.”

The archive teems with life. People could tell Helen Anrep things as readily as they did Vanessa Bell (whose 300 pages are themselves a limitless subject, including fierce denigration of the state of Monk’s House after Virginia’s death).

Dorothy Hepworth writes of her lover Patricia Preece’s bizarre, unconsummated 1937 marriage to Stanley Spencer: “as for the amorous injury, I do wish he had tried it on me, he would still be in hospital. I should have attacked him with the irons or anything I could lay my hands on. Oh how I wish he had done it on me! Patricia cannot bear to have it spoken about so I know you will keep it private.”

New vistas continually appear, as intellectually stimulating as they are vivacious, from the high comedy of the artist Claude Rogers’s wartime service to the tragic death of his contemporary Graham Bell (no relation) in a 1943 air-training accident. Bell’s long, wartime letters are brilliant, including a day in Essex with his girlfriend Olivier Popham (who later married Vanessa’s son Quentin). With others, they lay naked by a lake “like Adams and Eves before the fall. From time to time an aeroplane driven almost mad by the excitement of the naked body, swoops down, but as it cannot be proved that we are parachute troops and as they are British planes, they have not machine gunned us yet”; next day’s slow return to London finds a ravaged Bloomsbury, and guilt “at having missed what was the most horrible night in history”.

The archive, from the estate of Helen Anrep, is being auctioned by Gorringes (01892 619670) in Lewes on September 3 as one lot, estimated to £50,000- £80,000, with the separate sales of 13 oil paintings and a statue.