My friend Kerry Lee Crabbe, a playwright, screenwriter, lyricist and teacher, who has died aged 77, described himself as a “freelance human”.

A passionate belief in human rights was something he shared with Harold Pinter, a friend and mentor over several decades. This led to Kerry’s happiest experience: adapting Pinter’s novel The Dwarfs for the stage. It was filmed and screened on BBC4 in 2002 and produced at the Tricycle theatre in 2003.

At Cambridge University in the late 1960s, he acted (including as a memorable Playboy of the Western World), directed, and wrote plays and sketches for the Footlights. After university he became a trainee at Granada Television, and while there helped adapt Cat on a Hot Tin Roof (1976), produced by and starring Laurence Olivier.

For his play Rough Magic (1980), he was nominated most promising playwright by the Evening Standard, but despite critical acclaim, Kerry often felt his work never lived up to that promise and he had bouts of severe depression.

Despite this, he wrote and adapted several plays and 10 screenplays including Memoirs of a Survivor (1981), based on Doris Lessing’s novel. His favourite was The Playboys (1992), starring Albert Finney. Its producer, Simon Perry, has written that what made Kerry a fine writer of drama was his own human warmth, which he lent to his characters.

Kerry was born in Ipswich, Suffolk, to Joan (nee Mason), who worked for the Inland Revenue, and Lee Crabbe, a project manager for the design of farm machinery. He went to Ipswich school and then to Trinity College, Cambridge, in 1965, to study English.

As well as writing, Kerry was an engaged and inspiring teacher, first at the National Film and Television School and later for the Royal Literary Fund, the Open University, Kingston and Roehampton universities, the London Film School and London Film Academy. He also, increasingly, taught abroad, particularly enjoying his work in Africa, Asia and Cuba, where he was an honorary professor at the Latin-American film school founded by Fidel Castro and Gabriel García Márquez.

He wrote many song lyrics with his composer friend Daryl Runswick, writing, as he said (quoting Pinter), “with his left hand”. An album of their songs, One More Day (1981), was recorded by Cleo Laine.

Kerry’s first marriage ended in divorce, and his second wife died of cancer, as did one of his partners from his several other relationships. He never stopped caring for all his partners. You can’t just stop caring, he wrote to me, adding that his therapist said this made his life complicated. Humans are complicated, he replied.

He is survived by his sister, Bridget, and two nephews and a niece.