Thieves soil allotment paradise

Last night our shed at the allotment was broken into and our mower and strimmer stolen. We were alerted by an early morning phonecall from our friend James who walks his dog past our allotment every morning before work and noticed our shed door swinging open in the breeze. The police arrived to take a look, and found that 5 other sheds on neighbouring allotments and 15 on another allotment site nearby had also been raided. Luckily it turned out that the culprits were far from criminal masterminds and were arrested just a few streets away later in the day, and all the loot was found stashed in an empty house next to our allotment. After they'd been dusted for prints we brought the mower and strimmer home for the moment, while we consider how to make our shed even more secure. We'd already relocated the door hinges so they couldn't be unscrewed from outside and covered the window with mesh and wooden battens, so I'm not really sure what else we can do to deter thieves. Perhaps some extra reinforcement where the hasp attaches to the shed would be a good idea, we're also mulling over what would best sort of booby trap to install.