Simon Wills was a lutenist and continuo player, switching to the trombone after a hand injury. After a spell in the Teatro Massimo in Palermo he joined the London Symphony Orchestra and for 14 years was also principal trombone of the Chamber Orchestra of Europe. He played with the Fires of London in its last years, works regularly with the London Sinfonietta and at the Royal Opera House and has been a member of Endymion since the beginning.

He has a growing reputation as a conductor and as a controversial theatrical composer: his most recent opera, The Secret Agent, to his own libretto and adapted from Joseph Conrad's novel, attracted European-wide attention in its first run at the Feldkirch Festival in Austria. The surrealist pantomime A Day Close to Summer was commissioned by Baden Baden Festspielhaus to a scenario by Tatjana Gurbaca; a 'prequel' to Dido and Aeneas, its music was praised but its controversial content provoked a demonstration in the theatre. His Prelude and Fugue upon Quem Pastores Laudavere is a Christmas favourite in Germany (last year it was played by the Berlin Philharmonic).

He has been a professor at the Guildhall School of Music and Drama since 1986 and was elected a fellow in 2000. His main role now is as conductor of the the Guildhall Ubu Ensemble, a group devoted to the more extreme areas of the modern repertoire. He has been a visiting professor at the Conservatoire Superieure in Paris, Tallinn Academy, Almaty Conservatoire, North Texas State University and Sapporo Academy.