He first began his career working as a graphic artist and attended the Chelsea College of Art and Design. This was where he met his current life partner, Rima Horton. He also formed a design company with friends called Grafiti.

At 26, he wrote to the Royal Academy of Dramatic Arts where he was accepted after performing a speech from Richard the third at his audition. He spent 3 years at the school where he recieved the Emile Litter Prize, the Forbes Robertson Prize and the Bancroft Gold Medal.

Alan was involved in the Royal Shakespeare Company and did Shakespeare productions such as, As You Like It and Troilus and Cresside. He then took part in the production of Les Liaisons Dangereuses. The play would later go to Broadway, earning Alan his first Tony nomination and his leap into movies (he was offered the role of Hans Gruber - Die Hard, after Joel Silver saw the show).

Alan has done numerous theatre productions such as Romeo and Juliet, Antony and Cleopatra, As You Like It and Private Lives, only to name a few. He says theatre his his first love.

He made his directorial debut in 1997 with a play he had already directed called The Winter Guest starring long time friend Emma Thompson.

He is currently playing the ongoing role of Professor Severus Snape in the popular Harry Potter movies, as well as continueing to work in various big and small screen movies.