This may have actually been a service train...only it also included Test Car No 5. Now how often do you see an HST with a working pantograh? Note also that the power car's number was carried somewhat boldly on the front at this time. The train is seen here arriving at Leeds in 1989 we think.
Photo from James & Martin's Picture Collection Copyright 'Jampics' m.hawkes7@ntlworld.com