While working in a local garden we found this, the fin from a WW2 incendiary bombs which were dropped in their 1000’s in the areas. they were widely collected by boys during the war after raids as they were the only part of the bomb to survive

The German air force started the war using the 1918-designed one-kilogram magnesium alloy B-1E Elektronbrandbombe; later modifications included the addition of a small explosive charge intended to penetrate the roof of any building which it landed on. Racks holding 36 of these bombs were developed, four of which could, in turn, be fitted to an electrically triggered dispenser so that a single bomber could carry 1,152 incendiary bombs, or more usually a mixed load. Less successful was the Flammenbombe, a 250 kg or 500 kg high explosive bomb case filled with an inflammable oil mixture, which often failed to detonate and was withdrawn in January 1941.

In World War II, incendiaries were principally developed in order to destroy the many small, decentralised war industries located (often intentionally) throughout vast tracts of city land in an effort to escape destruction by conventionally aimed high-explosive bombs. Nevertheless, the civilian destruction caused by such weapons quickly earned them a reputation as terror weapons with the targeted populations.