Graham Short etched the motto “Nothing is impossible” which measures just a tenth of a millimetre. The letters are invisible to the naked eye, and can only be read with a medical microscope at 400 times magnification. It took Mr Short, 64, around 150 attempts before he was able to complete it.

Engraving at such a level requires almost superhuman effort and dedication to remain completely still. He was only able to work at night, when traffic vibrations are at a minimum, with his right arm bound to the arm of his chair with a luggage strap to minimise unwanted movement.

He uses a stethoscope to monitor his heart, attempting a stroke of the letter only between beats, when his body is perfectly still. He swims 10,000 metres a day and can slow his heart rate to 30 beats a minute.

He worked from midnight to 5.30am most nights of the week, for seven months on his razor blade. On a good night he’d manage three minuscule letters.

The Wilkinson’s Sword blade is now available to buy, with a £47,500 price tag.

Mr Short, a copper and steel engraver by profession, makes the dies used to print the green portcullis on House of Commons headed paper and the letterheads for the royal residences – Sandringham, Balmoral and Windsor Castle. He is, by his own admission, obsessed with miniature engravings. Weird hobby but very cool indeed.