A hundred years ago, John Galsworthy was one of the best known writers in Britain, and his play Justice had opened to enormous acclaim.

Galsworthy was at a party hosted by Lady Churchill, Winston Churchill’s mother, to bring the two men together.

Eddie Marsh, Churchill’s private secretary, asked Galsworthy: “If the Archangel Gabriel came down from Heaven and gave you your choice; that your play should transform the prison system and be forgotten, or have no practical effect whatsoever, and be a classic a hundred years hence, which would you choose?”

Galsworthy did not answer immediately but eventually gave the honest answer of the classic in a century’s time.

Stephen Plaice, writer in residence at Lewes Prison in Sussex at the end of the 1980s, discovered then that Galsworthy had obtained permission from the Home Office to visit Lewes Prison in 1909. This was so he could investigate solitary confinement.

He was shocked at the effect it had on many prisoners and called for its abolition, becoming even more forceful after a second visit to Lewes to interview men. Notes he took recorded their anguish.

The Home Office did not know he was writing Justice at that time and needed the research to complete his play, about a young prisoner being driven to the end of his tether by solitary confinement.

Plaice, who lives in Brighton, said: “What is remarkable about the play is the almost photographic realism with which Galsworthy captured the prison environment. Nothing seems to have escaped his attention.

“In fact, he seems to have imported the architecture and regime of Lewes Prison wholesale and undigested into his play.”

At the premiere of Justice in London in 1910, many members of the audience called for Galsworthy take a bow and stayed for more than an hour chanting his name, but the shy playwright had already left the theatre.

Galsworthy wrote to Churchill, who had just become Home Secretary, on solitary confinement and the two men struck up a postal friendship, before meeting at the party set up by Lady Churchill.

As a result, Churchill proposed reducing solitary confinement and it was soon abolished. He replied to Galsworthy congratulating him on his campaign.

Galsworthy became better known for other works, particularly The Forsyte Saga. He was awarded the Nobel Prize for Literature in 1932.

By then he was seriously ill and he died aged 65 from a brain tumour the following year. Refusing a knighthood, he was appointed to the exclusive Order of Merit in 1929.

He spent his last seven years in the secluded village of Bury near Arundel, where he could enjoy the beauty of the Downs. He was never poor, but by now he was extremely wealthy.

To meet his wishes after cremation, his ashes were scattered over the South Downs by aeroplane.

Several memorials exist to him including one by sculptor Eric Gill, another Sussex man, in New College, Oxford.

The Archangel Gabriel did not grant Galsworthy’s wish. Justice is no longer performed and his reputation has faded although many people still recall the TV version of the Forsyte Saga in the late 1960s.