This locomotive was built at the Sentinel Waggon Works at Shrewsbury in 1927. The 28 tons locomotive has a pair of transverse engines at the front and a vertical water-tubed boiler at the rear in the cab. It uses both gears and chains to transfer the drive to the axles. Unlike later Sentinel locomotives, it has only a single gear ratio.
Its central section houses a four inch thick cast-iron water tank to provide ballast as well as hold water. Whatever the water level in the tank, the weight distribution remains the same and so the locomotive is balanced front to rear.
This locomotive was delivered new to Croydon Gasworks. It was given the name Joyce after the daughter of Mr Sandeman, the chairman of Croydon Gas works where it operated for 32 years until 1960.
Late in 1927 it was tested by the LMS at Newton Heath. The tests demonstrated that the locomotive could haul a 1,000 ton load on the in an hour and a 250 ton load up a 1 in 40 gradient. It was found to use half the fuel of a similar capacity and that it could be ready to run from cold in an hour.
As a result of being impressed by the performance of 7109 the Somerset & Dorset Joint Railway purchased two similar engines for use at Radstock.
The locomotive was fitted with a new boiler in 1951 which is being refurbished as part of the restoration of the locomotive.
The preservation history of the locomotive is unclear but it is understood that it was moved to Bressingham in 1968. After this it moved to Steamtown at Carnforth in 1986.
It is thought to also have spent time at Tyseley and was under the ownership of the Industrial Locomotive Society for some time as well as being part of the Shropshire Collection for a period.
Before 2004 it was thought to be owned by a Yeovil group called the Somerset & Dorset Locomotive Owners.
Since December 2004 the locomotive has been owned by members (but not always the same ones) of the Somerset & Dorset Railway Heritage Trust (S&DRHT) and based at Midsomer Norton Station near Radstock.
The locomotive is currently being restored at Radstock by members of the S&DRHT.