After initially attending art college (SEEVIC) in Benfleet to become a book illustrator,[4] Whithouse decided to drop out of the course and turn to acting as a profession, training at the Guildhall School of Music and Drama.

He was a regular in the cast of the early 1990s BBC One drama series The House of Eliott and had a small role in the 1993 film Shadowlands.

Whithouse also appeared on stage in the West End, co-starring with Gene Wilder in Laughter on the 23rd Floor by Neil Simon in 1997.

"School Reunion", which featured the return of the robot dog K-9 and 1970s companion Sarah Jane Smith, transmitted on 29 April 2006.

[9] Later that same year (in November 2018) came the additional announcement that Neil Gaiman had hired Whithouse to collaborate with him, as the lead writer and Executive Producer on a television adaptation of Mervyn Peake's Gormenghast novels.

[11] The Whithouse/Davis piece published in August 2019 was an illustrated text story featuring the 1979 Marvel UK character Night Raven.

[12] In June 2023 it was announced that filming had started on The Red King, a mystery series from Whithouse commissioned by the channel Alibi.