John Gregson had never driven a car before making this film.
A replica locomotive was built on the chassis of a Bedford truck for the scene where the locomotive is seen driving down the road.
A wooden replica of "Lion" was made for the scene where "Thunderbolt" is removed from the museum.
Before deciding on the Camerton branch, also used previously for Arnold Ridley's "The Ghost Train", various other lines were considered including the former East Kent and Kent & East Sussex. Both of these former Colonel Stephens' railways have been preserved in part and now operate as privately-owned Heritage railways
For the sequence where the drunken Valentine and Dan drive a stolen locomotive through the streets of Mallingford, a replica locomotive was built atop a lorry.
The 'Thunderbolt' is a genuine veteran locomotive, its real name is 'Lion'. It was built for the Liverpool and Manchester railway in 1838, making it 115 years old when it was used in the film.
The credited driver, fireman and guard were not actors, they were British Railways employees from Westbury depot and were originally to be uncredited extras. After director Charles Crichton spoke to them on location and realized they "looked and sounded the part", they were given speaking parts.
The final scenes of Mallingford station were filmed at the Bath Road Bridge end of the main platform at Bristol Temple Meads station, Bristol, UK.
The locomotive, "Lion" was damaged during filming when the carriage train is reunited with the locomotive. The rear frame was bent by the force of the impact. The damage was still visible in 2001.
The name Titfield created by T.E.B. Clarke the from the adjacent villages of Titsey and Limpsfield in Surrey.
The role of the pre-accident locomotive #1401 was played by two separate 14XX locomotives, facing in opposite directions to allow as much filming as possible. #1401 starred as herself while #1450 masqueraded as her sister with identical number-plates. Though #1401 was later scrapped, #1450 was preserved and today operates on steam railways throughout Britain.
The veteran engine "Lion" was not able to accelerate above 15mph under her own power, so for many sequences the train would be propelled up to speed by one of the two 14XX engines, which would then brake sharply so as to not burst into shot.
Writer T.E.B. Clarke ("Tibby") was inspired to write the Titfield Thunderbolt saga after a 1951 visit to the volunteer-operated Talyllyn Railway, which carries passengers along the Cambrian coast between Tywyn and Abergynolwyn, in Wales. "The Titfield Thunderbolt" reflects Clarke's fascination with the volunteers' preservationist spirit there.
Writer T.E.B. Clarke was a neighbor of Richard Beeching, then Director of ICI, at the time of filming. Beeching's 1963 report "The Re-shaping of British Railways" resulted in the wholesale closure of many branch lines like the one portrayed in the movie.