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.

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.