Programme authorised on17th November 1949; built at Crewe Works and completed on the 3rd August 1951 to order E479/220/Swindon 397 and was withdrawn on the 30th December 1967. The additional part of the order number added the Swindon Works request to fit Western Region lamp irons and the Automatic Train Control equipment with in-frame pipework; this raised the cost of construction slightly to £20,144.
ALLOCATIONS: After running-in was completed to satisfaction and the ATC pick-up fitted by Swindon Works, 70021 was delivered to Plymouth Laira MPD (83D) to begin earning some revenue, and would have been the first of the five Britannias to see service from that depot. Early in 1957, the engine moved from Devon to join the other WR Britannias at Cardiff Canton (86C), but was removed from Cardiff after eighteen months and allocated to Trafford Park depot in Manchester (9A) from July 1958 until February 1961, when transfer to Willesden MPD (1A) came about. The engine resided at the West London depot until the first days of 1965, except for one week away at Aston shed (21D) in March 1962, which may or may not have been an anomaly. The locomotive then followed a very familiar path for the Britannia class; after closure of Crewe North depot (5A) to steam in June 1965 70021 was transferred to Crewe South shed (5B), but then deviated slightly when transferred to Newton Heath MPD (26A) in mid-July 1965. 70021 stayed in the Manchester area with a move to Stockport Edgeley depot (9B) in late May 1966, remaining there for slightly more than twelve months before its final move to Carlisle Kingmoor shed (12A) for its last six months in service.