Model of the 'Optimus' patent water closet, invented by Stevens Hellyer and made by Dent & Hellyer Limited, British, 1870

Invented by Stevens Hellyer in 1870, the ‘Optimus’ water closet or toilet was an improvement on earlier designs, flushing more efficiently and quieter. Raising the handle opens a large valve at the base of the pan and also turns on the flushing water. The flushing water runs for a time to ensure that the pan and valve are fully flushed. Keeping the flap clean was difficult but many toilets of this type were still used a hundred years later.

Hellyer was a campaigner for better plumbing, writing the textbook The Plumber & Sanitary Houses in 1877. Made by Dent & Hellyer, this model, which was constructed for a patent application, was donated to the Science Museum by the Earl of Cranbrook in 1961.