08/25/2008 at 01:00 AM EDT
Sipping cocktails at the bar of Mustique's Firefly hotel Aug. 7, Prince William
and Kate Middleton shared a quiet moment and took in the sunset. "They looked extremely happy together," an onlooker says. And why not? On break from the Navy before starting Special Forces training this fall, the prince and his love of six years wakeboarded and, along with Mick Jagger, attended a bash celebrating the private island resort's 40th anniversary. The weeklong holiday was the couple's third trip to Mustique—the perfect place, some Britons noted hopefully, for a royal engagement.