I fancy that shortly I might feel inclined to write the screenplay for a film, which already I am starting to think of as the new Brokeback Mountain.

It will be entertainment somewhat in the style of 1980s movie-makers Ismail Merchant and James Ivory – the pace leisurely, the detail meticulous. Think of their 1987 success, Maurice, which starred a youthful Hugh Grant. (His pals tell an amusing story concerning Madonna’s admiration for the film and her later thwarted efforts to meet its star.)

Maurice, of course, concerns the love that dared not speak its name; it’s a sort of gay version of Lady Chatterley’s Lover. Forster dared not speak its name, either, so having written the novel in 1913 he did not allow it to be published until 1971, the year after his death.

My film will concern Morgan Forster, the sight of whom, crossing the courtyard of King’s College, Cambridge, remains an unforgettable memory of my childhood. One could see why Lytton Strachey called him ‘the Taupe’ (mole).

In it I shall describe – or invent – a romance in which he becomes the love object of another man necessarily reticent about his sex life. This is Sir Roger Casement, the Irish diplomat executed as a traitor in 1916.

His so-called Black Diaries, detailing his many homosexual activities, came to light during the days before his trial and were once thought to have been forgeries, invented by the authorities to blacken his name and thereby reduce the risk of his being saved from the gallows. Only recently have tests proved them genuine.

The name for my film occurred before I even started the storyline. About it there is an oddly familiar ring, for it shall be called Morgan: A Suitable Treat for Casement.