In 1730, having purchased the Bell Inn on the Great North Road between London and York, he entered into a business arrangement with a farmer and cheese maker in Leicestershire to market a blue cheese exclusively from his inn at Stilton.

It quickly became known as "Stilton Cheese" and wagon loads of cheese were soon being delivered. Since the main stagecoach routes from London to the North of England passed through the village, Thornhill was well-situated to promote the sale of this cheese and Stilton's renown quickly spread far and wide.

"Cooper Thornhill" is now the acknowledged originator of the most famous name in English cheese. Today Stilton is a protected trademark and can be made only in the three Shires of Leicestershire, Nottinghamshire and Derbyshire.

In making Stilton, the cheese sits for at least five weeks before it is pierced with stainless steel needles to let the air in, allowing the blue to develop from the penicillium roquefortii culture which was added to the milk in the vat. In fact, the outside of the stilton is deliberately rubbed to provide a coat to stop the air from penetrating the cheese until it has matured. The difference between Stilton and Danish Blue, for example, is that Stilton producers make a cheese with its own flavour for five weeks and then blue it; Danish Blue is made as a blue cheese from the outset and has twice as much salt added to encourage the blue vein to grow. (Penicillum roquefortii thrives on salt.) That is why Stilton has one of the lowest salt contents of European Blues.

Another major difference is the veining. Stilton has delicate threads like a spider's web which meet in the centre from the piercing, whereas Danish Blue is spotted all over. Stilton also has a unique coat, the natural protective thin rind developed during the first five weeks to keep air out of the cheese. Furthermore, Stilton's curd is a golden straw colour rather than bleached white.

Finally, Stilton is one of the few cheeses in the world which is turned every day since the curds are not pressed to drain the moisture off and the moisture has to be evenly distributed. Thus Stilton has a unique mouth feel - full but light.

It is a creamier, smoother, less crumbly cheese with a golden colour and a less aggressive flavour. Though its flavour is stronger overall, it lacks the edge of bitterness or sharpness that is sometimes found in young Stilton. Its texture (it can be spread almost like butter) is achieved by aging the cheese longer under controlled conditions in which temperature and humidity are precisely controlled. Just as one chooses a certain wine to "lay down," the cheeses used for longer aging are picked for their keeping qualities, since not all cheeses are suitable for the extra month of maturation that is required. While any young Stilton can get older, it will not mature in the same way as the longer factory-aged Stilton since conditions in the distribution cold chain (under 5°C and very low humidity) cannot replicate factory conditions.

Mature Stilton has to leave the factory properly matured and only the very best vats of cheese are selected for maturing.