I don’t believe Tower Bridge would have been built without William Arrol.
He was clearly an exceptional man who had founded a boiler making company in Glasgow, Scotland and developed it into a global steelwork and engineering business.
He was fortunate in his location near the River Clyde which had become one of the major ship building centres of the British Empire. However he still had to make the most of this opportunity and he did so to such an extent that he progressed from a child cotton spinner to becoming the only civil engineer featured on a Scottish banknote.
What specifically did he and his company bring to the construction of Tower Bridge?
They had just completed two major railway bridges in Scotland which used significant amounts of steel, a relatively new material in civil engineering. The first was the Tay Bridge which had replaced its predecessor fairly quickly. That one had collapsed in a storm in 1879 with the loss of many lives and resulted in higher standards in structural rigidity to resist wind pressure. Arrol had managed to meet and possibly exceed these standards under immense scrutiny due to the human costs associated with the previous failure.
The second project has become a World Heritage Site: the Forth Railway Bridge. If English oak built its superior navy in the period up to the 19th Century, including Nelson’s HMS Victory, Scottish steel built one of the most memorable bridges of modern times. The civil engineers who designed it were John Fowler and Benjamin Baker. The latter was a close acquaintance of John Wolfe Barry and advised him no doubt on both the structural design of Tower Bridge and the need to use Arrol for the steel work.
It was a wise choice.