[1] Marsh was born in Truro, Cornwall and raised in Sennen, a Cornish village, and Woolwich, a district in southeast London.

His relationship continued with the BBC as a director and producer for three Arena series episodes, including the celebrated film Wisconsin Death Trip (1999).

[5] In 2008 he made the documentary Man on Wire, about Philippe Petit's walk between the Twin Towers of the World Trade Center in New York.

The film features Clive Owen, Andrea Riseborough, Gillian Anderson, Domhnall Gleeson and Aidan Gillen.

Marsh directed The Theory of Everything released in 2014, a biopic on Stephen Hawking starring Eddie Redmayne and Felicity Jones.