The toothbrush was invented in London’s most notorious prison
In the 1770s William Addis was serving time in Newgate for causing a riot. Brushing his teeth the same way as everyone else — in other words using a rag to rub them with soot and salt — he decided that there had to be a better way. Inspired by the sight of a broom, he took a small animal bone left over from his dinner and drilled small holes into it. Persuading a guard to fetch him some bristles, Addis threaded them through the holes and glued them in place. On his release the invention made him a fortune. His most expensive brushes used badger hair, while the lower end of the range featured pig and boar hair. His company, now known as Wisdom Toothbrushes, survives to this day.

From Mail Obsession: A Journey Round Britain by Postcode by Mark Mason and quoted in London Historians Members’ Newsletter, 09/2015.