Sentinel 4w vertical boilered tank locomotive built 1952, number 9535

A characteristic chain-driven Sentinel shunting locomotive powered from a high pressure vertical boiler, the technology developed for this machine by Sentinel at their Shrewsbury works owes as much to steam road lorries as it does to railways. The Sentinel was a radical attempt to modernise the steam shunting locomotive, and many were sold to this design, which at first glance could be mistaken for a contemporary diesel. This locomotive was one of a pair purchased by the National Coal Board for local collieries in 1952, number 9534 being delivered new to Holditch Colliery at Chesterton and number 9535 delivered to Silverdale Colliery. They were an unusual choice, but became stalwarts at their respective collieries while a selection of other conventional locomotives came and went. No other Sentinel locos were bought by the NCB for use in the area, and neither 9534 or 9535 were ever numbered or named.

Number 9534 fell out of use at Holditch by the end of 1965 and was scrapped there in August 1969. Number 9535 was more fortunate, for when it was last used in February 1968 it was laid up in at the end of a siding. Preservation came four years later and it arrived at Foxfield on 10 October 1972. Restoration to working order followed but it left the railway when its owner moved it for use on the Telford Steam Railway on 13 June 1981. There it received the name "F T Clamp" after one of the committed volunteers at Telford. Twenty years later it returned to Foxfield and has received some cosmetic attention but this important part of the Foxfield collection remains to be restored to working order again. It currently carries a maroon livery without nameplates, but has the maker's logo name painted on each side. It is known simply as "the Sentinel", as it probably always was.

Above: Sentinel 4wVBT 9535 at the end of its working life at NCB Silverdale Colliery in 1968 
 
The high pressure boilers of Sentinel products did not typically have a long life and some locomotives were later converted to diesel traction - see Thomas Hill diesel "BRC".