Stacy Keach as the eponymous detective in the television film Mike Hammer: Murder Takes All, 1989.Photograph: THA/Shutterstock

There have been few actors as inexhaustible as Stacy Keach, who has died aged 85. Throughout a long career that began in his childhood he was equally active in theatre, films and TV, moving from the sublime to the ridiculous and back again with aplomb. Perhaps it was his ubiquity and eclecticism that caused him to be so underrated.

Keach meant different things to different people. To theatregoers, he was a fine Shakespearean actor, acclaimed for his Hamlet, who was also adept in other classics and musicals (Barnum, Camelot, The King and I). To the filmgoer, he was one of the faces of Hollywood in the 1970s. To the television viewer, Keach was the tough private eye Mike Hammer, in the 80s TV series and spinoffs based on the novels by Mickey Spillane.