The engine was purchased by a Quainton Railway Society member, arriving at Quainton in December 1972, where it joined identical sister loco 2105, which is still at Quainton.

This locomotive was built by Peckett in 1948 to their 'Special R4' design (differing from their 'Standard R4' in that it was built to a smaller loading gauge). It was not delivered until 1951, to Croydon 'B' power station. It was joined here by its sister loco No. 2105, and Peckett 2103 (part of the same batch).

The R4 class are quite large four wheeled saddle tanks and they have a tractive effort of 12072lbs at 85% of the 180psi working steam pressure. The two outside cylinders have a 12 in. bore and the piston stroke is 20in. Valves are operated through Stephenson link motion with eccentrics between the frames. The coupled wheels are 3ft 0½in diameter and the engine weighs 23tons in working order, 19tons empty. Separately operated steam and hand brakes are fitted and the locomotive has a tank capacity of 690 gallons and space for 7 cwts of coal.

In the late 1960s, diesel locomotives took over at Croydon but No. 2104, along with No. 2105, was kept as a spare until 1972, when they were put up for sale. Purchased by a QRS member, it arrived at Quainton on 12th December of that year. It operated at Quainton for a number of years before being withdrawn for boiler repairs. No. 2104 moved to the Northampton & Lamport Railway in March 1989. It was the only operational steam locomotive at the Northampton & Lamport Railway. In 2017 the boiler certificate expired, and the loco is in store awaiting overhaul.

Current Location - Northampton & Lamport Railway, Chapel Brampton

References:
And Now - The Peckett Twins - The Class R4 - John Mortham - Quainton News No. 15 March 1973
2104 Steams Again - Quainton News No. 29 Autumn 1976