This balding, impeccably well-spoken London-born character actor made his name on the Shakespearean stage well before becoming a known quantity on television. Gary was the son of Austrian-Jewish émigrés Siegfried Waldhorn and his wife Liselotte (née Popper). As a youngster, he became enamoured with acting after seeing Richard Burton on stage as Henry V at the Old Vic. After graduating from the Yale School of Drama in 1967, Waldhorn made his theatrical debut as an extra in a National Theatre production of Rosencrantz and Guildenstern are Dead. For several years after, he served his apprenticeship as a small part supporting player. By the early 70s, Waldhorn had established himself as a serious actor, headlining as Milo Tindle in Sleuth (the part played by Michael Caine in the classic film version) at the West End. In 1972, he took the play on the road through Australia and New Zealand, along with Richard Todd, who essayed the role of mystery novelist Andrew Wyke. As a Shakespearean actor, Waldhorn later frequently performed with the Royal Shakespeare Company. Over the years, his roles have included Malvolio in Twelfth Night, Shylock in The Merchant of Venice, Leonato in Much Ado About Nothing, a highly acclaimed title role of Henry V (at the Old Vic, 1996-97) and the King of France in All's Well that Ends Well.

On screen from 1969, Waldhorn appeared in a variety of TV shows, his credits including perennial murder suspect William H. Druitt in the miniseries Jack the Ripper (1973), the diplomat and advisor Marquis de Caulaincourt in Napoleon and Love (1974), Conservative politician Henry 'Chips' Channon in Edward & Mrs. Simpson (1978), as well as recurring roles in the comedies All at Number 20 (1986) and Brush Strokes (1986). He also guested (usually as establishment figures) in diverse genre series, ranging from Space: 1999 (1975) to Robin Hood (1984) and from Rumpole of the Bailey (1978) to Lovejoy (1986) and Heartbeat (1992). In the final analysis, Gary Waldhorn will be most fondly remembered as David Horton, the conservative, wealthy, often starchy chairman of the parish council in the ever-popular sitcom The Vicar of Dibley (1994).

From April 1967 until his passing on January 10 2022, Waldhorn was married to Christie Dickason, playwright, poet, theatre director/choreographer, librettist and author of (to date) nine novels.