It was the abandonment of the agreement between LNER and LMS not to compete on the London to Scotland run that led to steam locomotion's finest hour. Two men, Sir Nigel Gresley and Sir William Stanier, would slog it out in a friendly but intense rivalry as they fought to build the fastest steam train in the land.

Specifications

			Coronation Scot		Mallard
	Length		22.6 metres		19.5 metres
	Weight		109.7 tonnes		103.6 tonnes
	Standard speed		90 mph		90 mph
	Record speed		114 mph		126 mph

Design

Both the Mallard and the Coronation Scot are designs based on the A4 Pacific class of heavy steam locomotive. The shared wheel arrangement of 4-6-2 is synonymous with the leviathan scale of engineering that was introduced to champion the lucrative long-haul passenger routes across the country.

The tubular, round-fronted body of a typical steam locomotive remained the basis for both of these incredible machines, but this was well hidden under the beautiful lines of the fashionable streamlined bodywork. The image created by streamlining captured the embodiment of speed and style associated with this pinnacle of the steam age. In truth, the extra weight (over two tonnes of steel) of the aesthetically curved panelling probably countered any aerodynamic advantage of increasing the top speed of the machines, unless they were permitted to travel for long distances without the necessary slowing down for stops. The real benefit of the design was that it appeared to lessen the amount of horsepower needed to accelerate to cruising speed therefore increasing efficiency.

Though both designers were producing some of their greatest work in creating these worthy opponents, it was LNER's Mallard creator Sir Nigel Gresley who recognised that better brakes would lead to shorter stopping distances and result in longer periods of high-speed travel.

Engines

The heart (and practically the whole) of any steam locomotive is the engine. The purpose of the engine is to pull a train of carriages, and to do this all that's required is a massive amount of power on wheels.

Working on an enlargement of his earlier Princess class, LMS designer William Stanier became obsessed by the concept of free-flowing steam for the Coronation Scot. He used nickel steel in the construction of the boiler and firebox to reduce weight and was very forward thinking in his redesign of the ratios between coupled wheels, pistons and valves.

At LNER, Gresley also followed this school of thought, relating to efficient free-flowing steam. His Mallard incorporated internal streamlining of components to obtain the best efficiency possible. Great efforts were made to engineer efficient methods of harnessing the energy from steam, combined with economical handling of exhaust. On 3 July 1938, with 250 pounds per square inch of pressure held in her boiler, the Mallard achieved a staggering 126 mph over Stoke Bank on the east coast line.