LONDON, ENGLAND - JUNE 09: John Mayer performs on stage at O2 Arena on June 9, 2014 in London, United Kingdom. (Photo by Rob Ball/Redferns via Getty Images)

LONDON, ENGLAND - JUNE 09:  John Mayer performs on stage at O2 Arena on June 9, 2014 in London, United Kingdom.  (Photo by Rob Ball/Redferns via Getty Images)