The small village of Coleshill was the centre of the British Resistance movement in WW2.
It was one the best kept secrets until the 1990's.
Apparently the secret agents had to go the Highworth Post Office and say the special codeword to be taken to the HQ at Coleshill.

see http://www.swindonweb.com/life/stranks.htm for more about the Post Mistress.