The stewardess didn't recognise the 24-year-old and turned down his request to enjoy the comfort and complimentary glass of champagne offered by the lounge.
Despite the snub, William refused to reveal his identity and went to the bar for a drink instead with three companions.
A spokesman for the ferry company P+O has confirmed the mix-up last month (OCT06), adding, "It is somewhat surprising that the stewardess failed to recognise him, and no doubt someone will be having a word with her."
Source: WENN