I am currently involved in a project about the Defence of the Firth of Forth estuary on the east of Scotland from the Napoleonic era until the end of World War II. At the moment I have turned my attention to U-boat activity in and round the Firth of Forth during WW I and WW II.Does anyone know if this subject has been covered by anyone? Is there any way of quantifying the amount of activity?

Many thanks for any assistance or suggestions.

Ron