By James Desborough Priscilla Presley discovered her husband’s infidelities while opening sacks of fan mail at their Graceland home. The besotted girls writing to Elvis made it perfectly clear, in stark, stabbing, black and white. From 1969, the king had been playing his comeback residency in Las Vegas and with gigs in Sin City came renewed adoration – and plenty of parties. It was the latter he began prioritising over Priscilla and their baby daughter, Lisa Marie, born the previous year, alongside his entourage known as the Memphis Mafia, run by pal and road manager Joe Esposito. Priscilla wa…