Matt Smith at Glastonbury
Monday, 28 June 2010 - Reported by Chuck Foster

However, a special unexpected guest appeared on stage to introduce the last song of the evening - none other than current Doctor Matt Smith! With a wibbly-wobbly timey-wimey arrival Matt roused the crowd and then joined the band for the performance.
Viewers in the UK can watch Matt's appearance and the performance on the BBC iplayer (from 1:50:22) for the next week.
A number of outlets have picked up on the story, including Gigwise, NME, Metro and the BBC.
And this article also mentions that Matt wasn't the only Doctor Who veteran to make a surprise appearance at this year's Glastonbury!