"I am just off to India ...", EM Forster wrote to his publisher in a letter disclosed for the first time yesterday, "I expect to have an interesting time and penetrate into queerish places."

Any double meaning is likely to be "subconscious, not intended - he's not talking like Oscar Wilde", according to Felix Pryor, literature specialist at the London auctioneers Phillips.

The writer was a diffident, ceremonious man unlikely to risk suggestive remarks to his upright publisher, Edward Arnold. All the same, the words he wrote in March 1913, at the age of 34, came true. In India and Egypt he did reach more deeply into his homosexual nature, as well as into other regions of experience, than ever before. Out of this came first his overtly gay novel Maurice - which he suppressed for nearly 60 years.

Before he set off for the subcontinent he wrote to his publisher: "I don't suppose you want a book about India, or do I know how to write one yet. Still, if you have any ideas on the subject, let me know ..."

Summing up his masterpiece A Passage to India with rare exuberance in a letter in 1924, the year it was published, he wrote: "Not 'gorgeous' East, but real East - complex, mystic ...I saw not only Anglo-Indian but also Mohamudans [sic] and Hindus".

The letters are part of a batch of 116, unpublished and rarely seen by scholars, which are expected to fetch up to £30,000 on March 30. All dating from the most productive phase of Forster's life, they are being sold by what the auctioneer calls a private literary source.

They cover 31 years of his bond with his publishers, beginning with his third novel, A Room With a View (1908). Shortly afterwards Forster wrote shyly offering to send three draft chapters of a new story "so that you could see a little whether it is the kind of thing you would care to be connected with".

"It is more ambitious than the last book ...Its title is Howards End". Howards End (1910) brought him "quite as much praise as it deserves" but also the first of a series of infuriating surplus apostrophes which still crop up 90 years later.

"I see that in some advertisements (eg in the Times) that the book is called Howard's End," he complained to Arnold. "I should be grateful if this could be rectified as I want people to realise that it is about a place not a person."

In April 1923 he wrote to Arnold diffidently offering 40,000 draft words of A Passage to India. A year later, with the book due out, he wrote: "I have been careful not to allude to contemporary politics ... but of course it describes the social soil out of which politics spring."