Monday 19 February, 20.00–21.00 on FIVE

Imagine having to move not just the contents of a house but the whole structure – brick walls, roof and all – in one piece, without it falling apart. Or imagine having to move trains through the air in the middle of a busy city centre. These are the types of daunting challenges facing teams of experts in this fascinating series. In tonight’s programme, two teams of experts face very different challenges. In London, 20 refurbished underground-train carriages must be placed in a tunnel that is sealed at both ends. Meanwhile, deep in the Canadian hinterland, a pair of aircraft enthusiasts are desperate to raise the remains of a Fokker plane that has sat at the bottom of a lake for 75 years.

Every day, more than three million people pile onto the biggest metro network in the world – the London Underground – so it is not surprising that it sometimes requires attention. After a five-month overhaul, the Waterloo & City Line is almost ready to re-open; all it needs are the trains. The problem is, this particular line runs along a tunnel that is sealed at both ends. The fact that neither Bank nor Waterloo has an easily accessible depot means that the carriages must be fed into the tunnel through a narrow hole in the street. “It’s 15 metres into the depot, and we’ve got to land the train onto rails which are only 7 centimetres wide,” says site manager John Chenery. “There is only one piece of machinery we can use in a situation like this and that’s a crane.”

The crane in question must be heavy enough to swing 23 tonnes of train carriage to its destination, but because the nearest possible location for it is a road 36 metres away from the hole, its substantial load must be swung in an intricate arc to avoid a nearby café. The threat of strong winds further complicates matters, as does the fact that the crane must be weighted with a massive 165 tonnes of ballast to counteract the weight of the carriage, all of which puts extra pressure on the road.

Once the operation is under way, project manager Alf Arnold looks on as a carriage dangles precariously above the site. “A million pounds is just floating in space,” he notes anxiously. Will the hydraulic struts prevent the street from caving in under the pressure? And can the team get the 20 new carriages onto the tracks without bumps – and in the right order?

This week’s second monster move involves a vehicle of a different kind. In December 1931, a lone transport plane flying equipment to a nearby gold rush flew into a snowstorm. The pilot managed to land the Fokker aircraft on the frozen surface of Lake Charron – but, as the crew escaped, the heavy equipment forced the plane to break and partially sink through the ice. A midwinter rescue was deemed impossible so the plane was abandoned and sank to the bottom of the lake as the ice melted.

Retired mountie and aircraft enthusiast Pat Madden is leading a project to recover the plane. “It’s an amazing saga of Canadian exploration and of aviation history,” he says. His wife Annette Spalding shares his passion, and the couple even spent their honeymoon looking for its remains. Using sonar to scour the 35 million square metres of muddy lake bottom, they finally discovered the skeletal frame more than 120 feet under water. Now all they need is good weather, a crack team of expert divers and a collection of aquatic robots to help winch it to the surface. Can they raise this important piece of Canadian history without damaging it?