After performing classic double-takes they blinked in disbelief.
Yes, the man hopping over a chainlink fence in a baseball cap was Edward Windsor.
But that was Edward the film producer not HRH The Prince Edward who was seventh in line to the throne.
There was no bowing, no naval escorts and definitely no pomp, unlike the scenes when his grandmother the Queen Mother arrived in Portsmouth only hours earlier.
That was Prince Edward, 32, trying to work incognito in an open-necked shirt and bomber jacket.
He was signed into the naval base as E Windsor and his film company colleagues referred to him simply as Edward.
The prince was in Portsmouth making part of a series for his film company Ardent which was commissioned by Meridian TV in Southampton.
The series – Crown and Country – featured historic towns and cities across the south and examined their link with royalty.
During their two days in Portsmouth the team filmed at Fort Nelson on Portsdown Hill and in the historic ships area of the naval base.
Edward made his TV production debut earlier that year.