Introduced in 1957 solely as a departmental machine, Ruston & Hornsby No. 20 (works no. RS408493) spent all its working life at Reading Signal & Telegraph department. Powered by a R & H 4cyl 88hp engine the motion was chain driven from a mechanical gearbox. The little machine weighed in at just 17 tons. Amazingly the veteran went on to be TOPS renumbered by BR, becoming 97020 in May 1980, but life expired the former No.20 was withdrawn in April 1981 and finally met its end some sixteen months later in August 1982. The locomotive is pictured at Reading on the 30th May 1972. Note the additional weights added to the sideframes. 
(Photo courtesy David Mant )