For the historian of early English Freemasonry, Lodge IV is the most interesting and important Masonic Lodge of all. Now called the Royal Somerset House and Inverness Lodge No.IV, it was first known as the Lodge that met at the Rummer and Grapes Tavern, Channel Row, Westminster and then - from sometime before 1723 - as the Lodge that met at the Horn Tavern in New Palace Yard, Westminster. It was one of the so-called 'Four Old Lodges' whose members met at the Goose and Gridiron Tavern in 1716 and agreed to form a Grand Lodge, an event which took place on 24th June, 1717. Unlike the other three 'Old Lodges' which were essentially Lodges of operative masons,1 Lodge IV - the most recently founded of the four - was composed of a new breed of Speculative Masons, to use the contemporary terms: 'Gentleman Masons' or 'New Masons'. The most influential members of the new Grand Lodge were all members of Lodge IV.