The Metropolitan Police Special Irish Branch was formed in March 1883 to counter Irish 'Fenian' terrorism on mainland Britain.
Over the years, Special Branch took on responsibility for combating a wide range of extremist and terrorist activity and the term 'Irish' was dropped from its title.
Special Branch had responsibility for gathering, collating and exploiting intelligence on extremist political and terrorist activity, disseminating intelligence for operational use and assisting other Government agencies to counter threats to the security of the United Kingdom.
Today, it has been restructured into the Counter-Terrorism Command.
Over the years, Special Branch took a keen interest in the actions and activities of certain British-based UFO researcher, such as Robin Cole (a Cheltenham-based researcher who dug deep into the UFO-related activities of the Government Communications Headquarters, GCHQ); Matthew Williams, best-known for his investigations of RAF Rudloe Manor, Wiltshire; Jonathan Downes; George King and a number of others.
The strange story is spelled out in all its weird glory within the pages of On the Trail of the Saucer Spies.