Incognito

Wax figures of the Prince and Princess of Wales at Madame Tussauds

"Prince William told me he had never been to New York before which, I must say, surprised me greatly.  I was even more surprised that the Duchess hasn’t been. I urged them to come back again incognito. New York is the type of city that turns a blind eye and would allow you to do that."
Patrick Stewart, quoted in The Guardian