Sir Nigel Gresley’s P2s were conceived to haul heavy trains over the Edinburgh to Aberdeen road. The original scheme combined the 2-8-2 wheel arrangement with an A3 boiler but this was subsequently worked up into a design with a longer firebox and double chimney. The 2-8-2s were the most powerful express passenger locomotives to run in Great Britain and their mechanical innovations were matched by their bold outward appearance. The doyen of the class, No. 2001 Cock o’ the North, was radically equipped with Lenz rotary valve gear, an ACFI feed water heater in place of injectors, a 50 sq. ft. fire-grate and streamlined steam passages to three cylinders which exhausted via a double Kylchap chimney. Gresley was greatly influenced by the work of the French engineer Andre Chapelon who had pioneered the use of these features and was determined to incorporate them in the P2s. Externally the design hid the tapered boiler in a parallel, elliptical cladding running from a V-fronted cab to a muscular, streamlined smoke-box (which incorporated integrated smoke deflectors), the whole affair sitting on a high running board which exposed the 6’2″ drivers entirely. The 220lb/sq in boiler fed three 21″ x 26″ cylinders and the locomotive developed a nominal tractive effort of 43,460lb. As a final touch Cock o’ the North was the first L.N.E.R. loco to carry a chime whistle.
Great care was taken with the design, including a mock-up of the cab – Gresley Society
Cock o’ the North is seen at Doncaster with the design team in 1934 – Gresley Society
The second member of the class, No. 2002 Earl Marischal, was fitted with Walschaerts valve gear and was equipped with additional smoke deflectors to compensate for the softer exhaust which resulted from its use. The final four members of this small class, No. 2003 Lord President, No. 2004 Mons Meg, No. 2005 Thane of Fife and No. 2006 Wolf of Badenoch, all appeared with an A4 front end coupled with the elliptical boiler cladding of the first two. Only No. 2001 was equipped with the feed water heater and this was removed when Nos. 2001 and 2002 were later rebuilt with the A4 nose.