IT DIDN'T take Sherlock Holmes to solve the big Splendour mystery, but a clue on Twitter certainly helped.

Alt-J, who had long been rumoured as the Sunday mystery act, sent out a tweet last night all but confirming their attendance at this weekend's event at North Byron Parklands, just out of Byron Bay.

"Anyone know what the weather is going to be like at Splendour this weekend?"

Triple J radio has since confirmed the United Kingdom band will be playing the Sunday, 6.40pm slot and that they will be airing the set live.

Hopefully, the guys from Leeds have packed their gumboots.