9. Robert Pugh
And the last GoT entry is Robert Pugh, who before playing Craster in the HBO series racked up an appearance as engineer Tony Mack in Silurian two-parter The Hungry Earth/Cold Blood.
However, he’d already appeared in the Whoniverse in Torchwood episode Adrift, where he played traumatised Rift victim Jonah.
10. Richard Briers
The late, great Richard Briers is another classic Who actor to appear in Torchwood, as the Chief Caretaker in 1987 Seventh Doctor story Paradise Towers and as millionaire entrepreneur Henry Parker in 2008 Torchwood episode A Day in the Death.