I see that John Osborne’s 1964 play Inadmissible Evidence has been revived to its usual ecstatic reviews. The Daily Telegraph’s critic said he had little doubt that the character was ‘ripped straight from the dramatist’s own mind and heart and set down on paper’.

I may be wrong, but I have always believed that Osborne took the storyline and his anti-hero Bill Maitland from a little-known 1959 novel Lawyer, Heal Thyself by solicitor Bill Mortlock. Note for a start the similar names. Both have divorce practices and lives filled with womanising, false discretion statements, contrived adultery, a client charged with importuning, alcohol and self-loathing. If I am right, Mortlock never received any credit for the ‘original story’.

But who was Mortlock, whose name does not appear in the Law List of the time? Born Frederick Moscovitch, he changed his name in 1937 to Frederick Evelyn Mostyn. After lecturing at the School of Law, he became a very successful solicitor with south-west London firm HCL Hanne & Co of Lavender Hill, opening its office in the Temple. Known as Lyn, he stood as the Labour candidate in a north London byelection; he co-wrote articles in the New Statesman with Michael Foot and advised Barbara Castle.

Before he became Mortlock, he had already published The Truck Act and Industry in 1950 under his own name of Mostyn. In the early 1960s, under his pseudonym, he went on to write a couple of textbooks on divorce including Marriage and the Law for the Law Society, and another novel, A Planned Coincidence. He then published nothing until 1991 when he produced a collection of short stories - Petition for Cruelty - about the absurdity of the divorce laws of the time.

I met him once through Tom Harper, who then edited New Law Journal, and we had lunch in a pub opposite the law courts. But so overawed was I to meet a writer (as opposed to a solicitor) that I can’t remember our conversation. My recollection is that he was friendly enough, but a somewhat austere man. He died in the 1990s.

Even if Osborne does not deserve my tag as plagiarist, Mortlock’s Lawyer, Heal Thyself deserves to be read as possibly the best legal novel ever - and certainly the best of its time.

James Morton is a writer and former criminal defence solicitor