The class B17 was a light yet powerful 4-6-0 express locomotive designed by Nigel Gresley for the LNER in the late twenties. They were to haul the heaviest express trains on the Great Eastern Main Line, but had to comply with the low axle load limits on the lines from London to Cambridge, Ipswich and Norwich. Specifically, they had been ordered as the Great Eastern class S69, now called LNER class B12, had become too weak. The first batch was built by North British and further batches followed from Darlington and Robert Stephenson & Co., what led to a total of 73 which were delivered between 1928 and 1937.

The boilers of the NBL batch were largely taken from the class K3 2-6-0 and the class O2 2-8-0. The cabs, cylinders and motion were taken over from the class A1 Pacifics. Only the outside cylinders drove the middle driving axle via Walschaerts valve gear and the inside cylinder drove the first driving axle via Gresley Conjugated valve gear. Most had tenders with a water capacity of 3,700 gallons, but some had larger 4,200 gallon tenders. Most locomotives carried the names of towns and the class was called “Sandringham Class” after the first locomotive, No. 2800. As some class members were named after football clubs, they were also nicknamed “Footballer Class”.

In 1937, No. 2859 “Norwich City” and No. 2870 “Tottenham Hotspur” were streamlined in the same manner like the A4 to haul the East Anglian. Between 1943 and 1957, most surviving class members received new type 100A boilers. Ten of these were rebuilt by Thompson into the two-cylinder class B2. The class was withdrawn between 1952 and 1960, with all members being scrapped. Today, No. 61673 “Spirit of Sandringham” is being built as a new locomotive by the B17 Steam Locomotive Trust.