The son of a Cornish mine captain was not simply an engineer - he was an inventor (his railway engines were running a decade before George Stephenson's) a visionary and a larger-than-life adventurer. But he still ended his life in poverty, wondering how it all went wrong.
The youngest of six children, Trevithick was born in 1771 and didn't show much early promise - his schoolmaster reported him as being "disobedient, slow and obstinate."
But he picked up his engineering knowledge by wandering around the mines where his father worked, and learned so quickly that, by the age of 19, he was being employed as a consulting engineer.
In the years before James Watt's steam-engine patents expired in 1800, Trevithick became involved in the search for a way to by-pass the separate-condenser patent which was costing Cornish mine owners a lot of money in royalties.
It was in 1797 - the year his father died and the year he married - that Trevithick made his first models of high-pressure engines.
In these, the steam from the cylinders was expelled to the atmosphere, doing away with the need for a condenser, circumventing Watt's patent and producing much more power. He called them "puffers" because of the noise they made.
A CORNISH engine house ... this one, still to be seen at Poole, near Camborne, once powered a whim which transported men and ore up the shaft.
Another road machine followed in 1803 which ran several times in London, before Trevithick turned his attention to railways.
His first machine ran on the normally horse-drawn line at Penydaren ironworks in South Wales in 1804, pulling 10 tons of iron and 70 men.
Unfortunately for Trevithick, he was a little ahead of his time. The cast-iron rails of the tramways of those days were just not strong enough to support the weight of his new-fangled machines and the Penydarren experiment was quickly abandoned
CIRCLE LINE ... Trevithick's Catch-Me-Who-Can giving shilling rides to customers at Euston, London, in 1808.
it was to be several years before the idea became commercially viable, but there is no denying the fact that it was Trevithick, and not George Stephenson, who was the real father of the railways.Stephenson and Trevithick certainly met at this time - a fact which was to become significant for the impecunious Cornishman many years later in South America.
An engine similar to the Penydarren one was built to Trevithick's specifications at Newcastle the following year. It seems highly likely that George Stephenson saw this machine and it is interesting to speculate just how much influence it had on the mind of the man whose name was to become synonymous with the Railway Era.
Meanwhile, new ideas poured from Trevithick's fertile mind - by 1808, he was giving rides at 1s (5p) a time on a circular railway he had constructed at Euston, in London.
He went on to design the highly-successful Cornish boiler, made improvements to his steam engine, designed agricultural machinery and even produced a Thames dredger. All that was lacking in Trevithick's make up was a proper business sense - he never fully capitalised on the work he did.
In 1816, Trevithick sailed to Peru to sort out problems with some engines he had sold to the silver mines at Cerro de Pasco. When he fell out with the owners, he travelled the country advising other mines and was rewarded when the Peruvian government ceded him some mining rights.
He had just begun to operate a copper and silver mine when he was called up to serve in Simon Bolivar's army. He was no soldier, but he did design and build a gun for the rebels before being released back to civilian life.
When he returned to his mine, the Spanish army overran the area and he had to flee. Eventually, after 10 years in Peru, Trevithick left for home and experienced many adventures crossing the jungles of the Isthmus before reaching Colombia, short of funds and half dead.
Who should he meet there but Robert Stephenson - the last time they had met was when Trevithick had dandled him on his knee during his talks with Robert's father. Stephenson gave him £50 to pay his passage home.
On arrival, Trevithick attempted to resume his engineering career, and the ideas began to flow again - but there was something inevitable about their lack of financial success. A petition to Parliament for a grant for his work in Cornish mines failed, and he died in April, 1833, in Dartford, where he was working on an engine.
The man who had given the world the high-pressure steam engine, the Cornish boiler, the railway locomotive, the steam dredger, the propellor and the threshing machine, among other innovations, would have been buried in a pauper's grave had his workmates not had a collection to pay for the funeral.
A few months earlier, he had written his own epitaph in a letter to a colleague: "However much I may be straitened in pecuniary circumstances, the great honour of being a useful subject can never be taken from me which, to me, far exceeds riches."