Sir William Arrol

From the outside, Tower Bridge appears to be built completely of brick and stone, but once inside, the skeleton of the Victorian beast reveals itself. Elaborate steelwork fills every space, held together by millions of rivets; immense cantilevered steel beams extend across the gap between the two towers forming the iconic walkways. But where did all this steel come from?

Inside the North Tower, you can see four august figures looking down from the window blinds. These are the engineers and designers who made this incredible structure a reality. One of these figures, Sir William Arrol, was the mastermind responsible for the 8km (5 miles) of iron and steel that form the Bridge's immense skeleton.

_{Top image: Forth Bridge in Scotland}

By the late 1870s the company had been renamed William Arrol & Co. It landed two high-profile contracts: the reconstruction of the railway bridge over the River Tay outside Dundee, which had to be rebuilt after its fatal collapse in 1879; and the now legendary Forth Bridge near Edinburgh, the first major crossing to be built entirely of steel.

Both steel bridges were at the forefront of Victorian technology, requiring construction techniques and methods of working that are still used today. Arrol also developed specialist equipment for the manufacture and erection of his steel components - this included the hydraulic riveters and cranes that were used during the construction of Tower Bridge. 

In the 1890s, William Arrol & Co became a globally active company, whose famous works include the Nile Bridge in Egypt, the Hawkesbury Bridge in Australia and the Warrington Transporter Bridge across the River Mersey in England. 

William Arrol & Co were also renowned crane manufacturers. They were contracted by the Harland and Wolff Shipyard in Belfast to construct a large gantry (known as the Arrol Gantry) for the construction of three new super-liners: the RMS Olympic, the RMS Britannic and the infamous RMS Titanic.

Arrol was also involved in the early days of the motorcar business, and with George Johnson, created the first motor vehicle constructed in the UK. An Arrol-Johnson car was the first motorised vehicle on Antarctic continent as part of Sir Ernest Shackleton’s 1907-09 expedition - sadly, the car proved useless in the harsh conditions and was never used.