River Esk appears outwardly much as built in 1923 by Davey, Paxman Ltd of Colchester. The design by Henry Greenly gave a locomotive capable of working heavy granite trains from Beckfoot Quarry to Murthwaite crushing plant and Ravenglass. The miniature one-third scale outline gave full protection to the driver while looking attractive on passenger trains.
Davey Paxman fitted their patent valve gear and Lentz poppet valves which gave problems. These were eventually solved by replacement with conventional Walschaerts valve gear and piston valves in 1928. This was done at the Yorkshire Engine Co. of Sheffield, who also fitted a separate 0-8-0 chassis under the tender, using their patent Poultney system to provide extra power for the stone trains. However, with the arrival of the Muir Hill petrol/paraffin locos, it was not needed and was removed in 1931. The old tender remained in use, raised high off the old bogies until 1970 when the current tender was fitted.
The loco was out of service from 1940-52 due to the need to fit a new firebox, but the original boiler shell continued in use until 1982. The loco is currently in black livery lined to the London and North Western Railway pattern.
River Esk was out of service from 2013 to 2018 following a fire in the workshop on 28 March 2013 as the locomotive was undergoing overhaul. Efforts to rebuilt the locomotive were led by engineer Nigel Day and it reentered service in 2018.