Born in Edinburgh, the tall, good-looking, strawberry-blond Glen became an actor almost by accident. While attending the University of Aberdeen, he was cajoled by friends into trying out for the school's drama society where he found his calling. After college, Glen enrolled at the Royal Academy of Dramatic Art (where his classmates included Ralph Fiennes, Jane Horrocks and Imogen Stubbs), earning the prestigious Bancroft Gold Medal in his final year. Almost immediately, he rose to prominence in Britain with an acclaimed turn as a charismatic gang leader in the TV-movie "The Fear" (opposite future wife Susannah Harker), followed quickly by a co-starring role on stage in Tom Stoppard's "Hapgood" (both 1988). Segueing to the big screen, Glen was cast as an American researcher in Kenya in the Dian Fossey biopic "Gorillas in the Mist" and portrayed the lover of a parliamentarian (Charlotte Rampling) in "Paris By Night" (both 1988). 1990 saw him undertake several leading roles and begin what seemed to be a promising feature career. His intense, physical inhabitation of a drug addicted murderer-poet in "Silent Scream" earned him accolades like the Berlin Film Festival Silver Bear. Glen also gave a well-received performance as 19th Century African explorer John Hanning Speke, searching for the source of the Nile, in Bob Rafelson's overlooked "Mountains on the Moon" while critics invoked comparisons to Peter O'Toole in reviewing his performance as an Irishman haunted by both the destruction of his family's home and a lost love in Pat O'Connor's "Fools of Fortune". He rounded out that auspicious year by playing Hamlet in Stoppard's film version of his play "Rosencrantz & Guldenstern Are Dead".
Rather than pursue a film career, Glen instead chose to concentrate on stage work. He acquitted himself in the title roles of "Hamlet", "Macbeth" and "Henry V" and also acted in "Coriolanus" and "King Lear". Displaying his musical talents, Glen undertook the lead in the Claude-Michel Schonberg-Alain Boubil musicalization of "Martin Guerre". In 1998, director Sam Mendes tapped him for the multiple roles in "The Blue Room", David Hare's riff on Schnitzler's "La Ronde". While co-star Kidman earned the lion's share of praise and notoriety for her blink-and-you've-missed-it nudity, Glen proved a stalwart match. Whether he would choose to trade on his newfound fame and return to features or be content treading the boards remained to be seen.