The ECW B51 coach body was one of the last coach designs built by ECW at its Lowestoft plant. Introduced in the early 1980s it was used by many National Bus Company divisions such as Cumberland, Eastern Counties, Eastern National, National Welsh, Southern Vectis, Shranrock & Ramber/Pilgrim Coaches, United Counties, Yorkshire Traction and London Country Bus Services (Green Line)

The body was must commonly fitted to either the Leyland Leopard or the later Leyland Tiger chassis, many of the NBC vehicles passed to independent operators in later life.

A double deck Leyland Olympian coach body was also built along side the B51 coach, dubbed the B45 it sold in smaller quantities to several NBC operators such at Eastern National, Maidstone & District, National Travel, United Automobiles & London Country Bus Services (Green Line)

Eastern Coach Works (ECW) can trace it roots back to 1920 when United Automobile Omnibuses set up a coach building business in Lowestoft. United's East Anglican operations were hived off to the newly formed Eastern Counties Omnibus, along with the coach building operations in 1931.

Eastern Coach Work became a separate company in July 1936 and was nationalised in 1947, becoming part of the state owned British Transport Holdings, it became a major supplier of vehicles operators with in the group.
Bus bodies were the main focus of the output with almost all built on Bristol chassis solely for the stare owned sector.

In 1965 a 25% share of the business was sold to British Leyland allowing ECW to supply private sector as well as the state owned operators.

ECW became a joint venture 50/50 owned by British Leyland & the newly formed National Bus Company in 1969. With the pending privztisation of the National Bus Company looming in the first half of 1980s, the NBC share was brought out by Leyland in 1982. The Lowesstoft factory & ECW business was closed in 1987.

The Oxford Diecast model depicts a 11 metre (36 feet) long body variant of the B51 fitted to Leyland Leopard & Tiger chassis, it was announced in February 2026 with the first release expected in the first quarter of 2027.