I have come across this link, and thought it might be of interest to anybody who will be in Cambridgeshire on Easter Sunday.
http://www.cambridge-design.co.uk/easteregg.htm
Just use your gps to find some easter eggs (vouchers for Thorntons eggs).
I don't work for the company concerned, but found the details mentioned in "Computer Weekly".
I have just noticed the press release was published on 1st April. The company concerned has some involvement with the SatMap.
Ivan