Complex sentence: Peter and Gordon both told Palmiere at the Las Vegas Festival for Beatles Fans that they were to perform at the 2006 Adopt-A-Minefield show with Paul McCartney, until it was cancelled by McCartney, himself, due to his impending divorce from Heather Mills.
Split into simpler sentences: Peter and Gordon told Palmiere at the Las Vegas Festival for Beatles Fans that they were to perform at the 2006 Adopt-A-Minefield show with Paul McCartney. However, the show subsequently cancelled by McCartney, due to his impending divorce from Heather Mills.