The TV villain, who plays scheming valet Thomas Barrow on the show, insists he's not a fan of his ""posh"" name, but he had to adopt it when he first started out.
Bosses at acting union Equity told him he'd have to change his name to avoid confusion because they already had a Rob Collier on their books.
He tells Out magazine, ""I said, 'Can I have Rob James Collier, and they said, 'Yeah, if you hyphenate it,' and I said, 'Well, can I have Rob-James Collier?' and they said... 'No, you have to hyphenate the James and the Collier'.
""I was like, 'That sounds like someone from aristocracy, as if I'm being somebody I'm not'. But they insisted.""