History series presented by Dick Strawbridge, in which a team of modern-day engineers is challenged to rebuild some of history's most impressive machines and to use their 21st-century knowledge to improve them. The team sets out to build a medieval machine gun known as a Ribauldequin. The toughest and most dangerous part will be casting the barrels, dealing with molten bronze in excess of 1,000 degrees Centigrade. They are also making bullets and playing with gunpowder. What could possibly go wrong?

This week, Dick challenges the team to build a catapulta, one of the most formidable weapons in the Roman arsenal. The Romans spent centuries perfecting their design of this enormous bolt throwing siege engine. The team have three days. Once proceedings are underway, Dick explains the original machine and reveals, with the aid of CGI, how this impressive weapon changed history.

The Byzantine flame-throwing boat boat once saved the Byzantine Empire from almost certain defeat, but the team is literally playing with fire when they construct it. The wooden boat is highly flammable and they are next to a vat of napalm!

The team work on the biggest build of the series – the Gothic Mega Crane. Its invention changed the skylines of Europe, enabling the building of towers higher than the world had ever seen. The team's blueprint is based on the design of the crane that built Salisbury cathedral, the tallest medieval spire in Europe. The crane is driven by two workers walking side by side to revolve a massive tread wheel housed within an even bigger frame. As the wheel turns, rope winds around the wheel's spindle, lifting the weight suspended from its arm. This technique allows the machine to lift blocks weighing as much as 700kg. The crew must build their crane in just three days and can only use materials to which the ancestors had access at the time. They are not merely matching the design, however, but also improving on it. Today, cranes have much more manoeuvrability and can reach further to pick things up, so the team decide to add the capabilities of a modern crane arm to their device. They also need to decide who is going to walk inside the wheel when the crane is complete in order to find out whether it works. No one seems keen... Almost as soon as the build is underway, Jamie and Owen disagree over whether speed or accuracy should take precedence when a sketchy chalk outline on the floor ends up being used as a template for the wheel. The enormity of the task ahead is becoming clear. While the workers battle on, Dick visits Salisbury cathedral itself for a spot of inspiration. This astonishing building was constructed from over 66,000 tonnes of stone and stands over 400 feet high. Halfway up the spire, he even finds the treadwheel that helped to build it. As the project progresses, the team discovers that the slightest miscalculation can lead to disaster. Danger is uppermost in their minds as two of them are locked inside the treadwheel powering the giant crane way above the ground – a job that lead to countless deaths centuries ago. Can the team r

The team set to work on the most explosive build yet – Churchill's Rocket Parachute. During the Second World War, Winston Churchill asked a secret team of scientists to come up with an ingenious way of making supply drops reach the ground quickly and on target. Troops desperately needed ammunition and equipment, and conventional parachute drops were constantly being shot down by the enemy or blown off course. What was needed was a faster, more accurate route from plane to ground. The scientists came up with the Rocket Parachute, in which three small parachutes would keep the load upright during a high-speed descent, and rockets would kick in to slowthe load down as it approached the ground. However, these retro-rocket tests ended in spectacular disaster. In some cases, the load even ended up being fired back into the air. Can the team succeed where WWII's greatest minds failed? They will only have one chance to find out whether they have got their calculations right when they drop their load from the sky. During the wartime trials, Churchill's scientists destroyed their workshop and injured members of the team. It will not be just the supply drop that the 'Beat the Ancestors’ crew needs to worry about! The blueprints Dick gives the team are based on recently declassified top-secret documents. In three days, the experts will need to make a pallet to hold the cargo, a rocket system, a trigger mechanism and a parachute. The cargo will be ammo boxes and an army-issue motorbike, which must land in a usable condition for the mission to be deemed a success. The team gets the chance to try out some small test rockets by fitting them into a simple wooden frame with bottles of water attached to it to increase the weight. When the rockets are ignited, the frame lifts up slightly, then flips over! Burn marks on the workshop floor reveal that one of the rockets did not fire – exactly the kind of situation experienced by the ancestors. As the team wrestle with t