Glen was founder and first Artistic Director of London Bubble Theatre Company (1972-1979), Chung-Ying Theatre Company, Hong Kong (1979-1982) and Artistic Director of Everyman Theatre, Liverpool (1982-1989).

Alongside founding and developing theatre projects, a freelance career has included directing many productions in the UK and abroad.Major regional theatre productions include Sheffield Crucible, Coventry Belgrade, Nottingham Playhouse and Bristol Old Vic. London theatres include Royal Court, Bush, Greenwich, Tricycle and Aldwych. Touring productions include Cambridge Theatre Company, Bill Kenwright Ltd and English Shakespeare Company (1990/91 production of Comedy of Errors) toured UK, Jerusalem Festival, the Ukraine and Moscow).

International productions (in corresponding languages) include: Blood Brothers for Shownote Ltd. in South Korea, Rhinoceros at Cameri Theatre, Tel-Aviv, Israel (Hebrew); Romeo and Juliet – Hong Kong Repertory Theatre, Hong Kong (Cantonese); Blood Brothers – Deutsches-Schauspielhaus, Hamburg, West Germany (German); Tugau – Rumpun Seri Drama Sarawak, Borneo (Bahasa-Melanau); Prometheus – Epidaurus Festival, Epidaurus Amphitheatre, Greece (Greek) (also toured Greece and Canada); five Shakespeare productions for Rhyming Theatre Company, Tokyo and Blood Brothers for Shochiku Company, Tokyo and Nagoya (Japanese). 

In 2017, Glen directed Willy Russell’s Shirley Valentine, starring Jodie Prenger, in a major tour to celebrate the 30th anniversary of the opening of the play.