[1][2][3] After graduating from the Webber Douglas Academy of Dramatic Art, he made his West End debut in 1963 with the comedy Shout for Life at The Vaudeville Theatre.

[4] Treacher then moved into television drama, making appearances in a number of classic series of the 1970s including Grange Hill, Bless This House, Minder, The Professionals, Dixon of Dock Green, Z-Cars and The Agatha Christie Hour.

[8] In late 1984, Treacher was the first actor to be cast in the BBC soap opera EastEnders, appearing in the first episode on 19 February 1985, as Arthur Fowler, a role he played for the next eleven years.

[9] Treacher said in 2015 that he was initially reluctant to sign up for the show as it meant long hours and a sizeable commute from his family home in Suffolk, but that he relented due to the chance of a steady income.

The character also endured a succession of misfortunes, which included two short spells in prison, a persistent struggle with unemployment, his daughter Michelle's (Susan Tully) pregnancy at the age of 16, his son Mark's (Todd Carty) diagnosis with HIV, and a midlife crisis where he had an affair with Christine Hewitt (Elizabeth Power) which almost broke up his marriage to Pauline (Wendy Richard).

He said the stress of a gruelling schedule working long hours on the show was affecting his health and that doctors told him that if he did not leave the job soon and relax, it would kill him.

[17] In 2015, Treacher told the press that he suffered from ataxia, a degenerative disease that involves poor muscle control, hindering his balance and ability to walk.