It was decided to hold a competitive tender for the InterCity 225 programme; this measure was aimed at avoiding the difficulties experienced with the APT programme. A pre-qualification document was formalised, in which various requirements for the type were laid out; these included the need to perform mixed-traffic duties (day and night passenger, parcel and mail, and overnight heavy freight services), the haulage of both tilting and conventional rolling stock, a top speed of 225 km/h, a maximum cant deficiency of 9° without the provision of tilt equipment, and that the maximum unsprung mass could not exceed 1.8 tonnes. Furthermore, BR stated its readiness to sub-contract with the successful bidder for the supply of technical information, advice and testing. The prequalification document was issued to BREL, Brush Traction and the General Electric Company (GEC), as well as the French firm Alsthom and Germany's Krauss Maffei. The inclusion of foreign manufacturers was in part due to the limited domestic experience with trainsets capable of such high top speeds. A total of three companies, ASEA, Brush Traction and GEC, submitted tenders for the design and construction of the Class 91 locomotive.