This topic might have a better name.
The actor was sometimes credited as Paul Marc Davies (for instance in TV: Utopia and sometimes as Paul Marc Davis.
Talk about it here.
Paul Marc Davis (born 16 April 1974[1]) played several characters for Doctor Who and its various spin-offs, both on television and for Big Finish Productions.
He has the unique distinction of being the only actor to appear in all three BBC Wales spin-offs, as well as Doctor Who itself.
He was interviewed on the Doctor Who Confidential episode 'Ello, 'Ello, 'Ello.
Credits
Television
Doctor Who
The Sarah Jane Adventures
Class
As Corakinus
Torchwood
Audio
Doom Coalition 2
Gallifrey: Time War
As Trave