The stained glass window shows keys from abandoned houses, and sections of the wall which prevents access to the land on which those houses once stood.
The key motif is actually taken from the keys to the prison in which John Bunyan was held for his open air preaching. The concrete blocks of the wall, could equally be the wooden panels of the prison door.
How fitting. The exhibition is being held in the basement of the John Bunyan museum in Bedford. The adjoining church is home of the stained glass window which shows part of the story of The Pilgrim's Progress and which was sent, in the form of a picture postcard, to Terry Waite when he was held hostage in Beirut.
(I've run several anti virusprogramms till late last night to shut my Trojan horse out, so, let's hope for the best...)