I was reading the Wikipedia article for the Class 57 and it mentioned...
How true is it that First Great Western ran these London to Plymouth/Penzance services with Mark 2 coaches?In 2000, Porterbrook placed an order for a prototype passenger locomotive fitted with electric train heating. This locomotive, 57601, was leased to First Great Western in June 2001, First Great Western were looking for a replacement for its elderly Class 47 locomotives. It hauled Mark 2 stock on day services from London Paddington to Plymouth and Penzance—until these ceased in September 2002—and on the Night Riviera sleeper service.