Rihanna, Mumford & Sons To Headline T In The Park 2013
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The Bajan Babe and the folk group will top the bill for the event between the weekend of 12th - 14th July, with the festival celebrating its 20th anniversary.
Speaking of their involvement, Alt-J said: "It's an absolute honour to be invited back to play at Scotland's biggest and best music festival - we can't wait!"
T in the Park festival director Geoff Ellis stated: "[It] seems like only yesterday that the first band took to the stage at Strathclyde Park for our inaugural T in the Park in '94.
"Now here we are in 2012, announcing two of the of the world's biggest and best acts to headline our 20th edition.
We have always worked incredibly hard to bring our T in the Park fans the best lineup possible, and this year is no exception. We are unbelievably excited that Mumford & Sons and Rihanna will be taking to the Main Stage in Kinross, as we are sure our audience will be.
"We have many more fantastic acts in store for everyone and will announce these next year, but it's shaping up to be one hell of a celebration."
A limited number of tickets will go on sale on Friday (December 7) at 9am.