When it comes to intra-city transfers, London is number one in English football.
When Petr Cech completes his move from Chelsea to Arsenal he will become only the fourth player to make a permanent move between the two clubs during the Premier League era.
Since the 1992-93 season, the Gunners have brought in two Blues players, William Gallas and Lassana Diarra, while only Ashley Cole has gone the other way.
With the two teams often tussling at the top of the table it's perhaps not surprising that they've been reluctant to exchange one another's players.
However, their fellow London clubs don't seem quite so fussy about letting their players move to their neighbours.
Petr Cech's Chelsea career in pictures:
A total of 286 permanent transfers have been conducted amongst London's 12 football league clubs since the summer leading up to the inaugural Premier League season of 1992-93.
That's an average of 23.8 per club, far more than that of any of England's other cities with multiple teams.
QPR have turned to other London clubs most often, having signed 44 players from other teams from the capital.
Millwall have signed 31, Crystal Palace 30, and both West Ham and Brentford have signed 29.
Birmingham's four major clubs, Aston Villa, Birmingham City, West Brom and Wolves, have transferred an average of 7.5 players each from their local rivals.
West Brom have picked up the most with 13 in total, made up of seven Aston Villa players and six Birmingham City players.
Which city has overseen the most intra-city deals?
Bristol's two clubs have transferred five players between them, an average of 2.5.
Manchester City have taken just two players from their city rivals, Owen Hargreaves and Terry Cooke, during the Premier League era, with Carlos Tevez only ever having been on loan at United.
The Old Trafford club have also taken two players from their local rivals.
Liverpool's two clubs have transferred just three players between them.
Gary Ablett moved from Liverpool to Everton, while Nick Barmby and Abel Xavier moved the opposite way.
Nottingham's two clubs also have an average of 1.5 players each, while Stoke's two clubs have an average of just 0.5.