It was forty years ago an unknown group took to the stage at The Dome in Brighton and thanks to that appearance were to become one of the best known and most successful groups ever.
They are of course ABBA who won Eurovision.
Well this weekend fans travelled to the groups home City and one of the group made a very rare appearance.
Tonight other members of the band will be in London for a special party.
Mike Pearse was at the special weekend event and has been meeting some of ABBA's army of local fans.