During the 1980s, prior to the reorganisation of BR from a regional production led railway to the business orientated organisation the planned rolling stock cascade for Exeter-Waterloo had always been towards HSTs-either as full 2+8 or 1+5 half units. 125 mph operation would never be realised but line speed increases to 100 mph or 110 mph and the high power to weight ratio of 2+8 the sets would have resulted in significant accelerations.
However, even with the East Coast electrification, changes in the InterCity Sector meant that IC125s would not now be cascaded as these are prime revenue generators, alternative modernisation schemes had to be developed. In the shorter term, Class 50 and Mk IIs could not survive as viable business options much beyond 1992 and alternatives demanded urgent consideration in 1988 to cover the next four to five years.
Double heading by both Class 33 and Class 50 was considered (platform lengths at Waterloo still prevent this) as was push-pull operation with Class 37/4 provided one at each end. Sustained 90 mph running would be on the limits of the traction motors as fitted to Class 37 even though of the same basic EE538 type as in Class 50, while the 85 mph maximum speed of Class 33 would no longer be acceptable.
One obvious solution was the use of Class 47/4s although this would bring in problems if its own. In October 1988 47473/547/587/589 joined the Class 50 pool at Laira. The fuel capacity limitation remained, so only particular duties were diagrammed for Class 47s rather than in a common user pool. No significant increase in availability resulted, and highlighted another difficulty-different braking characteristics showed up in higher brake block wear with the Class 47s needing reblocking during the third day of each three day diagram.
The ideal long fuel range (1295 gallon) Class 47/7 could not all be released from Provincial (Scotland) in May 1989, and increased InterCity Class 47/4 requirement meant that the better examples were converted to extended fuel range Class 47/8 by InterCity-operationally suitable but not available.
Class 47/4s had been diagrammed to certain Waterloo-Exeter line duties already-but never on the high mileage continuous turns. In 1984 0140 SX Waterloo-Exeter and 0643 SX return became the first regular duty on the line. Later, in 1986, 2100 Sun / 2210 SX Waterloo-Salisbury returning next day 0640 SX / 0700 SO Salisbury-Waterloo was diagrammed for a Bescot loco, while in 1988 one Bath Road diagram covered 0547 SO Exeter-Hove and 1105 SO Brighton-Exeter, and a second 0938 SO Plymouth-Brighton returning 1710 SUN Brighton-Plymouth.
Only Class 47/4s requiring major expenditure on F exams were left over-but Class 50s with more recent heavy classified repairs were still in service. The effect was that from May 1989 a pool of twenty Class 50 was created, along with eight 9-car and four 6-car Mk II sets to cover the entire Waterloo-Salisbury-Exeter service. At the same time this theoretically allowed NSE then to withdraw from the support of Class 33, and in the longer term from TC stock.
