The London Double Header began in 2004 and opens the season of the English Premiership (most recently known as the Aviva Premiership due to sponsorship), the top rugby union league in England.
Two games are played consecutively at Twickenham, originally involving the 'big four' London origin teams of the Premiership, Harlequins, London Irish, Wasps (London Wasps until the 2014–15 season) and Saracens. Harlequins were relegated from the premiership at the end of the 2004–05 season and thus for the 2005–06 season Leeds Tykes (now known as Yorkshire Carnegie) were included instead. The same applied to London Irish in 2016 who were replaced. The matches form part of the regular season fixtures, with one team nominated as the home side for each match. Since 2008 (2016 being an exception) and the inception of The Big Game, Harlequins only compete in the double header as an away side in order to reduce the number of home games they play away from the Stoop.
Since 2015 and Wasps' relocation to Coventry, the direction of the series has changed. Two London teams (normally London Irish and Saracens) act as the hosts with the away team being any of the other 10 Premiership Rugby teams. In 2016 Harlequins hosted due to London Irish's relegation from the premiership. In 2015, 2016 and 2017 the series would feature a newly promoted team.
At other times of year Twickenham is also used for regular season Premiership fixtures, such as The Big Game hosted by Harlequins at Christmas time, The Clash hosted by Bath and the Premiership Final in late May.