Founded as Ally & MacLellan, Glasgow in 1875 and then later known as the Sentinel Waggon Works Ltd, the company went through various place and name changes until in 1957 Sentinel (Shrewsbury) Ltd was obtained by Rolls-Royce. At that time Sentinel were producing steam locomotives and lorries, but the manufacturing of these vehicles ceased in 1958. In 1959, Sentinel produced a prototype diesel shunter which was operated on the military controlled Shropshire & Montgomeryshire Railway. In total 17 were produced and operated quite successfully during that year.
The 0-6-0 Sentinel was a larger version of their first 0-4-0 example. The first such 0-6-0 example was built in 1960, with full production beginning the following year with over 100 examples being built before the end of 1971. The locomotives were fitted with 8 cylinder 325 horsepower engines. So successful was the 0-6-0 design that the a further 36 examples were built in Lisbon by Sorefame, where they were designated the Class 1151.