I've been watching Alistair Petrie for some time now. It's easy to do because he's tall and ginger with a face you can – but should never – trust.
He specialises in minor characters who are also slimeballs. He played James Goldsmith in the superb TV movie Lucan and Sandy Langbourne in The Night Manager. He appears in various episodes of Midsomer Murders, Sherlock, Vera and Undercover.