Secret Societies in the UK?

Besides the obvious Freemasons, what are some other secret societies in the UK?

Well there's at least 3 (semi)secret societies in British universities that I can think of.

Pitt Club at Cambridge Uni

Bullingdon Club at Oxford Uni

The Speculative Society at Edinburgh Uni

Not sure about any others? In the 18th century there was the Hellfire Club, There also used to be an Irish one called The Fenian Brotherhood.

There's probably loads of them, but thing is they're secret.