Sir Derek George Jacobi, is an English actor and director, knighted in 1994 for his services to the theatre. Like Laurence Olivier, he bears the distinction of holding two knighthoods, Danish and British.

Jacobi, an only child, was born in Leytonstone, London, England to Alfred George Jacobi, who ran a sweet shop and was a tobacconist in Chingford, and Daisy Gertrude, who worked in a drapery store in Leyton High Street. His great-grandfather immigrated to England from Germany during the 19th century. His family was working class.Although a war baby, he claims a happy childhood. In his teens he went to the Leyton County High School and became an integral part of the drama club, The Players of Leyton.

At 18, he won a scholarship to the University of Cambridge, where he studied history. Other younger members of the university at the time included Ian McKellen (who had an "undeclared and unrequited" crush on him) and Trevor Nunn. During his stay at Cambridge, he played many parts including Hamlet, which was taken on a tour to Switzerland where he met Richard Burton. As a result of his performance of Edward II at Cambridge, he was invited to become a member of the Birmingham Rep immediately upon his graduation in 1960.

Jacobi quickly came to the fore, and his talent was recognised by Laurence Olivier, who invited him back home to London to become one of the eight founding members of the new National Theatre, even though at the time he was relatively unknown. He played Laertes in the National Theatre's inaugural production of Hamlet opposite Peter O'Toole in 1963, and Olivier gave him the role of Cassio in his 1965 film of Othello and of Andrei in Three Sisters in 1970.

After eight years at the National Theatre, Jacobi left in 1971 to pursue different roles and mediums of expression. In 1972, he starred in the BBC serial Man of Straw, directed by Herbert Wise. Most of his theatrical work in the 70's was with the touring classical Prospect Theatre Company, with which he undertook many roles, including Ivanov, Pericles, Prince of Tyre and A Month in the Country.

Although Jacobi's name was becoming known and he was increasingly busy with stage and screen acting, his big breakthrough did not come until 1976. It was the title role of the BBC's blockbuster series I, Claudius that finally cemented his popular reputation with his performance as the stammering, twitching Emperor Claudius winning him many plaudits. In 1977, thanks to his international popularity he brought Hamlet on a tour through England, Egypt, Sweden, Australia, Japan and China. He was then invited to play it at Kronborg Castle, better known as Elsinore Castle, the setting of the play itself. In 1978 he played in the BBC's production of Shakespeare's Richard II, with Sir John Gielgud and Dame Wendy Hiller. In 1980 Jacobi took the leading role in the BBC's Hamlet, made his Broadway debut in The Suicide, and then joined the Royal Shakespeare Company (RSC) from 1982 to 1985 where he played four demanding roles simultaneously: Benedick in Shakespeare's Much Ado about Nothing, for which he won a Tony; Prospero in The Tempest; Peer Gynt; and Cyrano de Bergerac. In 1986, he made his West End debut in Breaking the Code with the role of Alan Turing. The play was taken to Broadway. In 1988 Jacobi alternated in West End the title roles of Shakespeare's Richard II and Richard III in repertoire.

In 2001, he won an Emmy by mocking his Shakespearean background in the television sitcom Frasier episode "The Show Must Go Off", in which he played the world's worst Shakespearean actor: the hammy, loud, untalented Jackson Hedley. This was his first guest appearance on an American television program. His TV career saw him measure with Inside the Third Reich (1982), where he played Hitler; Mr Pye (1985); Little Dorrit (1987), from Charles Dickens's book; The Tenth Man (1988) with Anthony Hopkins and Kristin Scott Thomas.

Jacobi continued to play Shakespeare, notably in Kenneth Branagh's 1989 film of Henry V (as the Chorus) and as Branagh's director in the Renaissance Theatre Company's production of Hamlet. The 1990s saw Jacobi keeping on with repertoire stage work in Kean at the Old Vic, Becket in the West End (the Haymarket Theatre) and Macbeth at the RSC in both London and Stratford.

He was appointed the joint artistic director of the Chichester Festival Theatre, with the West End impresario Duncan Weldon in 1995 for a three year tenure. As an actor at Chichester, he also starred in four plays, including his first Uncle Vanya in 1996 (he took a second run in 2000). Jacobi's work during the 90's included the 13 episodes series TV adaptation of the novels by Ellis Peters Cadfael (1994-1998) and a televised version of Breaking the Code (1996). Film appearances included performances in Kenneth Branagh's Dead Again (1991), Branagh's Hamlet (1996) as King Claudius, in John Maybury's Love is the Devil (1998), a portrait of painter Francis Bacon, and as "The Duke" opposite Christopher Eccleston and Eddie Izzard in a post-apocalyptic version of Thomas Middleton's The Revenger's Tragedy (2002).

In March 2006, after 27 years together, he registered his civil union with long-term partner Richard Clifford, four months after such unions became legal in England and Wales.