It was NOT James Watt that invented the high-pressure steam engine. James Watt made very useful improvements to Newcomen's low-pressure steam engine, while several people experimented in the following years with high-pressure steam. It was Richard Trevithick, however, who invented the first proven, high-pressure steam engine, particularly in his Pen-y-Darren locomotive.

Richard Trevithick was the inventor of the Steam Engine.

Richard Trevithick is considered to be one of the pioneers of railway travel. His biggest development to railway travel was the high-pressure steam engine.

How to turn steam into power, he invented the very first steam engine.

Richard Trevithick, 1804