Trengrouse was born in Helston in Cornwall in 1772, and worked as a cabinet-maker. However after he witnessed a shipwreck on the Cornish coast in 1807, he decided to find a way to snatch sailors from ships wrecked on the rocks and sand bars off Cornwall.

According to legend, the solution finally came to him when he attended a firework display in honour of King George III. He wondered whether a large rocket fired from a sinking ship could pull a rope across hundreds of yards of water onto the shore. His famous rocket apparatus, and later the Bosun's Chair, was born.

Unfortunately, he couldn't interest the British government in his idea, but the Russian Tsar recognised its worth after trials had been carried out in the Baltic and the Black Seas. He sent him a diamond ring and assured him that if he came to Russia, he would give him practical support. But Trengrouse declined, apparently sending a message stating "My country first!"

Trengrouse didn't give up and eventually the British government ordered a few of his "Life Saving Apparatus". However he was double-crossed. Government engineers examined the design and decided to manufacture their own version. Trengrouse was given a measly £50 in compensation. By 1841, he was almost destitute and he died penniless in 1854.