William Morgan Sheppard, best known for his work in Star Trek: The Next Generation the series and subsequent Star Trek films, died Sunday. He was 86.

His son, actor Mark Sheppard (Lost Voyage) shared news of his father’s death in an emotional tribute on Instagram.

The London-born actor began his career on the stage. He was an Associate Artist with the Royal Shakespeare Company for 12 years, and appeared on Broadway in 1966 with Marat-Sade and later in 1975 with Sherlock Holmes. But it was his portrayal of Dr. Ira Graves in 1989’s Star Trek: The Next Generation series for which he became known to audiences worldwide. He also went on to play the Rura Penthe commandant in Star Trek VI: The Undiscovered Country in 1991, Quatai in the Star Trek: Voyager’s 1999 episode Bliss, and the chief Vulcan Science Council minister in 2009’s Star Trek film.

His other credits include an episode of Doctor Who, in which he starred as Old Canton Delaware alongside his son Mark. He last appeared on the screen in 2016’s drama Last Man Club and in fantasy series The Librarians that same year.

Additional film work includes 2007’s Transformers, and 2008’s Over Her Dead Body, and guest roles on Dexter and It’s Always Sunny in Philadelphia.

Sheppard is survived by his wife, son Mark and three grandchildren.