The prototype’s life on the WR started in December 1974 when the set was delivered to Old Oak Common following an extensive overhaul and modification. The early part of 1975 was spent on test running and crew training, including one timing run Paddington to Plymouth and return in January with a similar run to Penzance in March. The set entered traffic on 5th May 1975 and operated throughout the summer, but on some days its diagram was covered by loco and coaches, especially on Saturdays.
5/5/75-5/10/75
M-F – OOC-B Pkwy>07.45 B Pkwy-Padd>10.15 Padd-WSM>13.47 WSM-Padd>16.45 Padd-BTM>BTM-OOC
SO – OOC-WSM>07.57 WSM-Padd>11.45 Padd-BTM>15.30 BTM-Padd>18.45-BTM>BTM-OOC
The set was used on a special run from Kings Cross to York to celebrate the opening of the National Railway Museum at the end of September 1975, but suffered a significant power car failure, that required a works visit. This delayed the sets entry into regular working on the South Wales route by a month. It took up its regular diagram from 3/11/75, but as previously there were days and sometimes weeks where the set was absent for maintenance/repair. There was no diagram for Saturday working in the October 75 timetable.
06/10/75*-02/05/76 *03/11/75 in actuality
M-F Ecs OOC-Swdn>Swdn-OOC>09.00 Padd-Swan>12.52 Swan-Padd>16.45 Padd-BTM>19.15 BTM-Padd>OOC
Just before the end of this timetable period the set was stood down and the power cars returned to Derby Works. They then spent the summer of 1976 periodically employed on a test train consisting of Mk 3 production vehicles and a MK 3 loco hauled vehicle, testing the trailers P8 tyre profile. These tests came to an end mid-August 1976.
Due to the slow delivery of production HST sets, it became apparent to the BR that there would barely be enough commissioned sets to launch the WR interim 125mph service from 4/10/76. As part of the contingency it was decided that the prototype set would be used on 1 of the production sets regular diagrams. The set was reformed mid-September 1976 and after a short period of crew training in South Wales, was in traffic on the first day of the inaugural Inter-City 125 timetable. It was confined to the following diagram and remained in service for a month..
4/10/76-05/12/76
M-F OOC-Padd>08.00 Padd-Swan>12.00 Swan-Padd>16.00 Padd-Swan>20.00 Swan-Padd>Padd-OOC
SO OOC-Padd>08.45 Padd-BTM>11.30 BTM-Padd>15.00 Padd-Swan>19.00 Swan-Padd>Padd-OOC
SUN OOC-Padd>09.45 Padd-BTM>13.30 BTM-Padd>16.45 Padd-BTM>21.00 BTM-Padd>Padd-OOC
At the beginning of November 1976 the set was permanently stood down as enough production sets were available to cover the 8 diagrams that constituted the initial service. It’s last known working was on 3/11/76. The set languished in the carriage shed adjacent to Old Oak’s HST shed through the winter of 76/77. That is until the power cars were moved to Derby for overhaul in mid-February 77. The trailers were then stabled at St Philips Marsh for a period but were eventually stored at Worcester from May 1977. Subsequently, trailers were moved to Derby for conversion for other use.
Hope this helps.