A few of the Hastings Motor Cars were used in temporary formations with BR test coaches.
I don't know if they were through wired for multiple working or if the rear vehicle was just dragged but using these probably worked out cheaper than using locomotives and gave the ability to use local drivers who were not passed out on locomotives
This is another one of the imaged from Modern Locomotives Illustrated No 218 at St Pancras station in 1987.
The vehicle in the middle was ADB975032,Test Car Mars and was an ex Class 501 which was used for various traction tests.
It is seen sandwiched between 1066 which was formally 1002 and even though this is an all departmental unit it is still an unusual combination
Image Key Publishing/Colour-Rail
On the London Transport Museums Website there are these 4 images taken by Peter Wilson of the Motor Cars from 1003 flanking test car DB999550 on the Underground.
They are taken at Parsons Green on the District Line with an R-38 stock approaching on a Tower Hill service, if you want to find out more about these pics go to the LT Museums website and put DEMU into the search
Another one of the same combination is from Ian Allens, British Rail DMU's & Diesel Railcars by Brian Morrison shows the combination at Colchester open day in May 1988
We also have some images of some Hastings Motor Cars heading through Reading.
They are in a separate article so instead of reproducing them here click this Link
Something in the Railway Modeller in August 1986 was a couple of shots of this formation, this time it has Lab 10, RDB975428 along with DB999550
Another one which could be claimed to be on Underground territory is 1003 seen with 999550 at Wimbledon.
It is seen at Platform 4 in Wimbledon and even though it can be argued that this is British Rail metals the platform its in is one of the 4 used only by the underground
This is another one of the imaged from Modern Locomotives Illustrated No 218 and probably taken the same day as the LT Museum collection
Above, the motor cars from 1006 have been borrowed to haul the high speed track recording car which is normally hauled my locomotives
The entire formation is seen leaving London Bridge station
Image by John Law
one of the most unusual combinations to run must be this one which is seen in Locomotives Illustrated No 231
1066 was used a lot with London Undergrounds Track recording car 999666, this vehicle was modified with standard main line hight couplers so it was also told it had through wiring so both ends could be used in multiple.
This was the only Underground vehicle which was registered for the main line, I know your going to mention the District and Bakerloo lines run over BR Track but there special dispensation was given to run where this vehicle could run anywhere on the national network and like the Hastings vehicles given Code 0 gauge clearance so they could run anywhere.
Image from Key Publishing/Colour Rail
Modern Locomotives Illustrated No 218 is all about the Thumpers and they have a few images Im going to use here.
This shot also dates from August 86 so is probably the same formation as the shot above shows it being powered by 1018 as it passes Cheriton near Folkstone
Image by Rodney Lissenden/Key Publishing