4-2-2

The 4-2-2 configuration offered designers eight wheels to spread the weight of a larger locomotive, but prior to the bogies (invented in the 1830s) becoming popular, created a long rigid wheelbase with limited adhesion.

Daniel Gooch built 29 examples of his Iron Duke express locomotive class for the Great Western Railway between 1847 and 1855.

On the GNR, Patrick Stirling built 53 examples with outside cylinders at Doncaster Works between 1870 and 1895, for use on the East Coast Main Line between London King's Cross and York.

They ran at an average speed of more than 60 mph (97 km/h) during the race to the north, and were called eight-footers because of the driving wheel, that was more than 8 ft (2.4 m) in diameter.

Additionally, each driving axle of a locomotive had to be supported on large plain bearings, with required further lubrication, introducing a potential point of mechanical failure through overheating and a considerable source of friction.

With only one driving axle, a 'single' had much less rolling resistance than a four-coupled engine, requiring less steam to achieve a given speed and also being more free-running when coasting downhill.

The Stirling 'eight-footers' were very successful, but were best suited to the predominantly straight and flat GNR main line in Cambridgeshire and the Vale of York.

However, in 1886 Francis Holt, manager at the Derby Works of the Midland Railway invented a practical form of steam sanding gear which allowed locomotive crews to quickly and effectively stop wheelspin.

This led to the Midland reviving the 'single' in the form of the distinctive inside-cylinder "Spinners"; eighty-five were built to five designs by Samuel Waite Johnson between 1887 and 1900.

Other notable UK examples of the 4-2-2 include the GER Class P43, which was an early oil-burning engine, developed by the pioneer of oil-boilers, James Holden.

Ivatt Class A5 singles of the GNR, designed before the Great Central engines, continued to enter service during 1901, being the last of their type to take to the rails in Britain.