It was paid for by King George III, who granted £4,000 for it to be made,[1] and £200 a year for its maintenance, although the telescope remained Herschel's property.

Just prior to them entering the open mouth of the tube, the King commented "Come, my Lord Bishop, I will show you the way to Heaven!

[3] The first was cast in a London foundry on 31 October 1785,[4] and was made of speculum (an alloy of mostly copper and tin) with arsenic to improve the finish.

Over a year was spent grinding and polishing the mirror; however, Herschel found it to be "much too thin to keep its figure when put into the telescope"[4] (despite weighing half a ton).

The object I viewed was the nebula in the belt of Orion, and I found the figure of the mirror, though far from perfect, better than I had expected.

[1] Herschel described the view of Sirius through the telescope:[3] "... the appearance of Sirius announced itself, ... and came on by degrees, increasing in brightness, till this brilliant star at last entered the field of view of the telescope, with all the splendour of the rising sun, and forced me to take the eye from that beautiful sight."

As part of the funding deal with the telescope, Caroline Herschel was granted a pension of £50 per year to be William's assistant.

[2] The tube, which fared better as it was made from iron rather than wood,[2] was left lying horizontally in the garden, supported by stone blocks at either end,[2] still containing the second mirror as well as some of the machinery.

When John Herschel moved from Observatory House to Hawkhurst in 1840, a number of items (including the 40-foot telescope) were left behind.

In an inventory written at the time, he recorded "In the Observatory, beneath stair, one 40-foot mirror, with case and cover."

The mirror was rediscovered on 2 February 1927: "All that could be seen on a casual inspection was a somewhat rusty iron ring, about 4 feet in diameter and 5 inches thick ... covered in front with a close-fitting lid of thin metal.

The iron ring, which was not unlike the tyre of a cart-wheel, was obviously the cell of a large mirror and was quite separate from the tin cover.