GNR Large Boiler Single

The GNR Large Boiler Single, more properly known as the Stirling 8-foot Single, was the most celebrated express locomotive of the Victorian era: Patrick Stirling's inside-cylinder 2-2-2 (and later 4-2-2 with leading bogie) single-driver express engines built at Doncaster Works for the Great Northern Railway between 1870 and 1895, with driving wheels of 8 ft 1 in diameter — the largest coupled driving wheels ever fitted to any British express locomotive. The Stirling Singles defined express railway travel in Britain for a quarter of a century and made the East Coast main line between London King's Cross and Edinburgh one of the most celebrated railway routes in the world.

Patrick Stirling designed the first Single in 1870 with a conviction that large driving wheels were the key to express speed — that the long stride of an 8 ft wheel at relatively low piston speeds would give smoother, faster, and more efficient running than smaller wheels turning faster. The No. 1 of 1870 was a simple, clean locomotive of extraordinary elegance: a domeless boiler (Stirling refused to use a dome, believing it aesthetically and mechanically inferior), outside cylinders in an unusual Stirling arrangement driving the single large rear-mounted wheel, and the GNR's apple green livery with the large wheel at the centre of the design's visual balance. The result was one of the most beautiful and iconic Victorian locomotives ever built.

In service the Stirling Singles were formidably fast. In the Race to the North of 1888 and the even more celebrated Race to Edinburgh of 1895, the Stirling Singles working the GNR's portion of the East Coast route between King's Cross and York achieved speeds that astonished contemporary observers. On 22 August 1895, during the climax of the 1895 Race, GNR No. 668 ran from King's Cross to Grantham — 105 miles — in 101 minutes, an average speed of over 62 mph including the Stoke Bank climbs. These performances established the East Coast as the premier British express route and made the Stirling Singles famous throughout the railway world.

Forty-seven Stirling Singles were built between 1870 and 1895, and all gave front-line express service until their displacement by Ivatt's Atlantics from 1898. The last examples were withdrawn between 1908 and 1916. One locomotive, No. 1 — the original Stirling Single of 1870 — was preserved by the Great Northern Railway itself and is now at the National Railway Museum in York, where it is one of the most significant objects in the national railway collection.