After leaving university Liam held a variety of jobs. He worked as a fork lift operator at Guinness and even as a truck driver. He took on a position at a teacher training college in Newcastle (UK) for two years. It was in 1978 that he first worked in films. Liam portrayed Jesus Christ for the film Pilgrim’s Progress. He won roles for the Lyric Players’ Theatre in Belfast. Liam was with the Lyric Players for two years before he moved to Dublin. He was offered a part in a production at the Project Arts Centre and took on several projects with them.

In 1980 John Boorman, a filmmaker saw Liam in the role of Lennie Small from the play, Of Mice and Men. John Boorman offered Liam a part in the Arthurian movie Excalibur. After portraying the character of Sir Gawain in Excalibur Liam moved to London. In London, Liam continued his work on the stage as well as television and low budget films. Between 1982 and 1987 Liam also starred in five films in all. He took a starring role alongside Anthony Hopkins and Mel Gibson in The Bounty, and was working with Robert De Niro and Jeremy Irons in The Mission.

Liam decided to move to Hollywood in 1987. It was his ambition to work in high profile roles. 1987 saw him star with Cher and Dennis Quai in Suspect. His role won critical applause. International recognition was won with his performance in the Steven Spielberg film Schindler’s List. His portrayal of Oskar Schindler brought an Academy Award nomination for the Best Actor. He also won nominations for this role with the BAFTA’s and Golden Globe Awards. It was Schindler’s List that was to establish Liam as a leading actor in Hollywood. Some of his other famous period films include Rob Roy and Michael Collins. Michael Collins earned Liam a nomination for a Golden Globe and he won the Best Starring Role at the Venice Film Festival.