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Of all the engines we’ve bought over the years, few have had the sheer presence of this USRA Heavy Mikado. A magnificent machine - over eleven feet long with tender and weighing in at 1300 pounds - it’s caused one or two people to mistake the 7 ¼ inch gauge Black 5 sitting next to it in the workshop for 5 inch gauge!

A one-owner engine, it’s come to us direct from the builder, a retired gentleman who served his apprenticeship with British Railways from 1958 to 1961, followed by a lifelong career in engineering.

With a 7 ¼ inch gauge Black 5 and A3 already under his belt, a holiday in the USA led to the decision to build an American prototype.

The Heavy Mikado was a highly successful design by the United States Railway Administration, the nationalised railroad system set up in the First World War to oversee design and production of standardised locomotives and rolling stock. Produced in large numbers in the post-war years, the model represents one of a batch built by Baldwin for the Southern Pacific Railroad in 1919.

Drawings and a complete set of castings were ordered on his return home, marking the start of a six year build.

Given the sheer size of the model, the quality of work and detail contained therein, it’s difficult to know quite where to begin with this one. Suffice to say that the consensus from all who've driven it is it’s one of the those engines once driven, never forgotten. Docile, powerful, instantly responsive to the throttle – an engine very obviously designed and built to do a job of work, in both full size and 7 ¼ inch gauge. The thing feels like it could pull a house down!

The welded steel boiler was supplied new by Bell Boilers in 2009 – it’s pressed to 125 psi, features four radiant superheaters and a firebox tubeplate that you can only just reach with an arm stuck as far as your elbow through the firehole door.

The three safety valves are commercially produced fine-scale items, imported from the USA. We’ve had them apart for inspection and service, they are works of art inside, with a fine-toothed ring gear permitting adjustment of the pop characteristics, as in the full size.

Water feed is by a pair of Mr Holroyd’s estimable injectors; an effective duplex steam pump which runs beautifully at a prototypically correct speed, and a high capacity double-acting hand pump in the tender. Typical of the builder’s attention to detail, its handle is stored on the tender in rubber-lined clips to stop it rattling about.

The boiler has had internal examination followed by hydraulic and steam tests with new certification issued. It’s in good condition, run with water treatment from new. We fitted a new fusible plug, there’s a spare dome gasket included (the speed of our new laser cutter is still a novelty - if you’re cutting one gasket you might as well cut two!)

The chassis runs on roller bearings, the engine pushing along with little more effort than a Romulus, despite its abundance of wheels. Fit and finish of machined parts is excellent, the robustly proportioned motion work and valve gear typical of the type. Wheels are cast iron with EN24T steel tyres.

Locomotive and tender bogies are highly detailed castings - we had the rear one off for boiler test to give better access for removing the fusible plug, it's a substantial assembly requiring two people to remove safely.

The engine was built for serious hard work and easy maintenance, witnessed by details such as the extended lubricator tank, allowing for a day’s continuous running; quick detach connector under the cab floor for filling the boiler, and provision for compressed air start.

There is a scale whistle atop the firebox in front of the cab – currently disconnected, as leaks from the whistle valve were found to impair forward vision when driving. It’s of little consequence – the “real” whistle lies under the nearside running board, a fabulous four note chime, reproducing the pitch and harmony of the original. It’s the first time we’ve had a model where you feel the whistle as well as hear it!

The engine has a working headlight, with running lights to locomotive and tender – we love the beautiful lost-wax cast “divers helmet” running lamps. The turbo generator runs up to speed making all the appropriate noises but, despite having the box of electronic tricks from its supplier, is something the builder never actually managed to make work - it remains a project for somebody more adept in the electrical black arts...

Both locomotive and tender are fitted with vacuum brakes, the locomotive vacuum reservoir slung under the nearside running board aft of the cylinders with a PNP brake cylinder mounted between the frames.

The builder states that no corners had been cut, no expense spared in the construction of the locomotive; having spent a good deal of time looking over it in the workshop in recent weeks we can’t disagree. A tribute to a fine engineer, its running numbers on the smokebox record the year of his birth, the dollar piece riveted to the smokebox door an authentic – if not strictly prototypical – piece of America.

Complete with a set of drawings and toolkit for operating and running maintenance, including a plate which, clamped between crosshead and cylinder rear cover, positions the motion for setting the valves. The boiler has original manufacturer's documentation along with comprehensive club history.

Supplied complete with firing irons, oil and water treatment. We would be more than happy to give half a day's instruction on the steaming, running and disposal of the engine to a new owner if required.