The 36 Ton 275 H.P. Diesel-Hydraulic Ruston-Hornsby Type LSSH No.459515 was amongst the last of the locomotives built by that firm at their Lincoln Works before they were taken over by the General Electric Company.
It was supplied on 13 April 1961 to the Central Ordinance Depot C.O.D. Bicester as part of the War Office contract 4/KH/H/044/DC14/P/1961 for locomotives to be used in Major Army Depots. It then moved to C.A.D. Bramley on 3 June 1961, remaining there until 26 January 1970 before returning to 32 Central Workshops, Bicester for a short spell.
Six months later on 13 July 1970 it reurned to Bramley and stayed until 16 June 1980, when it was transferred to the G.E.C. works at Newton-le-Willows for a general overhaul which included a replacement diesel engine (Paxman V6 Type 6RPH No 56782). After rebuild on 16 July 1981 it was issued to C.O.D. Donnington where it was in regular use until December 1989 when it was withdrawn from use and placed in storage pending disposal, and finally put up for sale in March 1991.
The locomotive was then purchased by several of the Association Members (including Don Moore - who's wife IRIS - she is named after) and finally arrived at Chinnor at the Rugby Cement Works siding on Wednesday 09 October 1991 on a lowloader from the Army C.O.D. Unit at Donnington in Shropshire.
IRIS is still performing the function she was purchased for and fulfills a wish made in the early days of the Association to provide the Railway with a complete Engineering train, consisting of a locomotive, crane, tool van, flat wagon and brakevan.