91002 entered traffic in April 1988 and went straight into testing on the East Coast Main Line, hauling test trains comprised of Mk.2 and Mk.3 stock, before being delivered into Bounds Green for operational use from the middle of June that year.

From Autumn 1989, British Rail started naming the Class 91 fleet and on 4 May 1993 91002 received the name 'Durham Cathedral', which it carried until February 2009.