The towering German centre half arrived at the Emirates Stadium back in 2011, as manager Arsene Wenger looked to add some stability to his back line after being on the wrong end of an 8-2 thumping to Manchester United. The £8m they spend to bring the German international in from Werder Bremen now looks like a bargain, with the 29-year-old a mainstay of the Gunners defence.
But Mertesacker, formerly of Hannover, arrived with a reputation for being slow, cumbersome and error prone, which many Arsenal fans felt was the last thing they needed following that thrashing to United.
However, Mertesacker has gone on to prove them wrong during his time in North London, producing consistent displays - as well as leadership - to help make a once porous Arsenal defence much stronger.
And now the German, who looks set to feature for Joachim Loew's side at the World Cup in Brazil this summer, has praised the Gunners faithful for their continued support, even when times get tough - making a mockery of suggestions that Arsenal fans are fickle.
The interview below was filmed for the BBC, and Mertesacker opened up about his time at the club, as well as the famous 'BFG' nickname he has picked up.