When David Mitton held the director position, Steve held a number of different positions on the show. These positions consisted of Second Unit Director (first season), First Assistant Director (second season), Production Supervisor (third season), Models Supervisor (fourth season), Assistant Director (fifth season), Associate Producer (sixth season), and Programme Consultant (seventh season).
Asquith directed the sixth season episodes Jack Jumps In and A Friend in Need. He then became the show's main director after David Mitton's retirement and remained in that role until 2008 when production moved to Nitrogen Studios. After which, Greg Tiernan took the director's position.
In an interview with SiF, Asquith mentioned that after his work on Thomas ended, he applied for a job as a letter sorter.