My explanation of Shawbridge is a bridge is a spanner as it spans across the river, and definitely is sure (Shaw). And it is in the southern half of England. I may not be right but I think it is bridge rather than a tool type of spanner.
thats ok bibblebub. When I was a teenager I flew from Lydd to Le Touquet in a Carvair, with a car in the middle of the aeroplane and passengers sitting by the windows. Those were the days!