Mine-laying Hampden

The Handley Page Hampden was a twin-engine RAF bomber used mostly in the early years of World War II. Until spring 1940, British practice was not to use its bombers to actually bomb anything, but to drop propaganda leaflets on German cities and a few real bombing missions on the German fleet.

In addition, Hampdens were used laying mines in areas frequented by the German naval ships. Those missions, called “Gardening,” increased with the German invasion of Norway. It should be mentioned that British and French forces were en route to invade Norway, but the Germans got there first.

Wikipedia says, “(T)his activity proved highly effective, experiencing a low casualty rate of less than 1.9 aircraft per mission.” For every 10 Hampdens sent out for Gardening the North Sea, two would not return, on average. “Highly effective” does not count if you are aboard one of the two.

https://en.wikipedia.org/wiki/Handley_Page_Hampden#Specifications_(Hampden_Mk_I)

Damned Good Show gives a good account of an RAF squadron flying the Hampden.