Royce Mills was born in Tetbury, Gloucestershire. Originally studying fine art he went on to train as a theatre designer at the Guildhall School of Music and Drama, during which he decided upon acting as a career and graduated in 1967, receiving both the gold medal and the Shakespeare Prizeman Award.

Mills made his home in the theatre, starting his career at the Yvonne Arnaud Theatre in Guildford where he both acted and occasionally designed shows, notably for Sandy Wilson's The Boyfriend. He followed this production into the West End at the Comedy Theatre. Other theatrical appearances included The Bed Before Yesterday, Run For Your Wife, See How They Run, The Seven Year Itch, and The Phantom Of The Opera. After appearing in The Forest he became a regular with the D’Oyly Carte Company at the Savoy Theatre. He also appeared in a number of pantomimes for the festive season, making a name for himself as dame Widow Twankey, often back at the Yvonne Arnaud.

His television career began back in 1964 with an appearance in Crossroads; his first major role was as P.C. Dinkie Dinkworth in the 1971 comedy series Copper's End. Other notable roles included Uncle Peter in Come Back Lucy, Ken in Rings on Their Fingers and Andrew in Minder. He made numerous guest appearances in a variety of comedy shows in the 1970s starring the likes of Morecambe and Wise, Mike Yarwood in Persons andThe Les Dawson Show, and ensemble shows such as The Cut Price Comedy Show and the Kenny Everett Television Show.

His vocal talents could be heard on the radio, notaby on the satirical show Week Ending, and on many commercials. His voice is, of course, most recognisable as a voice of the Daleks during the 1980s.

He was a serving council member of Equity for a number of years.