The reformed group had been reluctant to play any open-air festivals
The band - including Christine McVie - played London's O2 last night (May 27)
Buckingham made the comment at an event in Los Angeles on Wednesday (April 29)
Stevie Nicks tells crowd that drummer was throwing up backstage
Band will tour Britain and headline Isle of Wight festival later this year
Band also add dates in Birmingham, Leeds and Glasgow
Band will headline Sunday night of next year's festival
The band will play at London O2 Arena on June 26
Band will now play Manchester Arena on July 1
Tickets for the band's 2015 tour went on sale this morning (November 14)