[3] It was an improvement on earlier designs because it had two fireboxes, instead of one, and this allowed it to steam more freely.

In 1870, Fairlie invited guests to witness Little Wonder in a trial against the Festiniog Railway's existing locomotives Mountaineer and Welsh Pony.

Little Wonder hauled a train of 112 wagons weighing 206 tones up the line at an average speed of 12 1/2 mph.

Welsh Pony was only just able to haul a train of 26 wagons weighing 73 tons at a maximum speed of 5 mph.

[5][unreliable source] This article relating to steam locomotives operated in the United Kingdom is a stub.