He certainly wasn't unknown to me. I'd already seen him in I, Claudius (Lucius Aelius Sejanus), Dune (Gurney Halleck), and Lady Jane (Henry Grey). The only one of those in which he had a noticeable amount of hair was in I, Claudius.And yeah, Patrick was a virtual unknown to American audiences in 1987, TNG put him on the map. Only LeVar Burton and Wil Wheaton were names at the time.
Lest we forget Lifeforce and Excalibur!