How do you get a steam train on stage?
A theatre production of The Railway Children returns to Waterloo Station this month - with a genuine Victorian steam train in a starring role. But just how do you get a fully-operational locomotive centre stage?
Like a veteran actor, Stirling Single No.1 - all 66 tonnes of it - relaxes in the wings before making its big entrance in a cloud of steam.
The train is the scene-stealing star of The Railway Children, which is back at Waterloo's former Eurostar terminal after an extended run in 2010.
"It's the only real thing in the show, so it had to be authentic," says producer Matthew Gale, as we take a seat in a luxurious carriage behind the locomotive.
The Olivier-award-winning production sees comedian and broadcaster Marcus Brigstocke in the role as Station Master Perks.
The old Eurostar platforms have been converted into a 1,000-seat venue with the audience seated on either side of the railway tracks.
"The theatre was designed for the show. It's quite an extraordinary space," says Gale. "When the audience walk into it you see them go quiet."
The steam train only appears at key moments, and is shunted into the heart of the action by a diesel engine that remains out of sight.
The green and black Stirling Single No.1 locomotive made its stage debut in the York Theatre Royal and National Railway Museum production of The Railway Children in York in 2008.
The engine was built in 1870 by the same workshop that produced Flying Scotsman.
For its return to the London stage it was carried by lorry from York to Southall where it was put on the tracks and shunted to Waterloo.
"There's something very human about a steam train and the noises it makes," says Gale.
"I'm not a train buff, but there is an emotional connection to trains, and in particular to steam trains. It's part of our heritage, and part of our childhood memories."
He adds: "Marcus Brigstocke as Mr Perks jokes about being upstaged, but in reality nothing overwhelms the story - which is told by the human actors."
E Nesbit's story is known to many through the classic 1970 film version, starring Jenny Agutter and Bernard Cribbens. An 1871 saloon coach that featured in the film also appears in the stage show.
The success of the UK show has led to an identical production in Canada. The Waterloo theatre space has been recreated in a giant tent next to Toronto's CN tower. Another British steam engine was shipped over for the production.
As any regular rail traveller will know, trains don't always stick to the timetable. How reliable has the Stirling Single No.1 been on stage?
Gale touches the highly-polished teak of the Victorian saloon. "Obviously, the fear has been that the train won't run on time, but it's been fine.
"There are a lot of people involved maintaining the train - there are daily safety checks and practice runs. Trains built in the 1870s were pretty reliable."
He adds that there are seven different safety levels to ensure the train can never run out of control in the auditorium.
But does the noisy 21st century world of Waterloo Station ever intrude on the play?
"There are times when you can hear a train rolling by," says Gale. "We have a big soundscape in the show, but being in a real station adds to the atmosphere."
The Railway Children is showing at Waterloo Station until January 2012