There are actors, when you see them, that cause you to say, "Hey, it's That Guy. You know, from that show, and that other show, and this movie. I can't remember his name off the top of my head but I know his face."
Mr. Postlethwaite was not exactly one of those. He was a British character actor who had a way of standing out in supporting roles. The first time I saw him was in Baz Luhrman's "Romeo + Juliet". He played Friar Laurence. The friar is one of the most well intentioned persons in the play, but his best efforts are set at naught and I have seen him portrayed as kind but ineffectual. Mr. Postlethwaite's friar was a man of conscience and determination; Fate had to work hard to overcome his efforts to make peace between warring families. His was the most interesting performance in the film for me. I always noticed his solid performances in any film I saw him in, no matter how small the role. His other big Hollywood part was in the second Jurassic Park movie, as the hunter who wanted to bag a T-Rex. The T-Rex didn't stand a chance.
Farewell Pete Postlethwaite. My sympathies to your family and friends.