[quote=Doppleganger]Well the 'Polish-British Common Defence Pact' was specifically aimed at any agression by Nazi Germany towards either country. Given how far away Poland was from Britain though, there were clearly other reasons for signing this pact.quote]
I reckon you'll have to look in the corner of geopolitics. Germany had already gained the Rhineland, Austria and Sudetenland. At that time the article written by Sir Halford John Mackinder, a renowned British geographer, about the "The Geographical Pivot of History" was widely accepted. The statement made by hime was:
Who rules East Europe commands the Heartland
Who rules the Heartland commands the World-Island
Who rules the World-Island commands the world
The British politicians couldn't afford to sit this one out at home. I mean there are elections to be one, and some believe that you have to be "manly" once in a while to do so.