No this is not an April Fools story. According to a new book The Sunday Times reported:
Cleo Rocos, who co-starred in The Kenny Everett Television Show, reveals in The Power of Positive Drinking how she, Mercury and Everett dressed Diana in an army jacket, black cap and sunglasses before venturing into the Royal Vauxhall Tavern in south London.
“When we walked in . . . we felt she was obviously Princess Diana and would be discovered at any minute. But people just seemed to blank her. She sort of disappeared. But she loved it,” Rocos says.