Peter Harrison is a retired medical practitioner who has had a lifelong interest in military architecture and has written 11 papers over the last 15 or so years on diverse subjects for Fortress, Fort, Casemate and Postern. He has written on fortified churches in La Thierache in France, Peloponnesian castles and fortresses, the fortified village of Ushguli and the Pa Maori. Boydell and Brewer published his book Castles of God: Fortified Religious Buildings of the World in 2004 and it was short listed for the Longman-History Today Book of the Year Award in 2005. It has also been translated and republished in Italy.