There has been an increase in shed and garage burglaries:

Access to garden – have a locked gate
Fix trellis to the fencing to deter people climbing over
Lock shed using a closed shackle padlock
Burr screws on hinges to prevent unscrewing
Install a motion sensor shed/garage alarm
Large items like mowers & bikes to be chained down
Security mark property
Is it necessary to store high value items within outbuildings?
Secondary access points should be secured. If no longer used then permanently fix shut
Consider installing CCTV
Consider installing security lights with motion sensors
Place car close to garage doors to prevent entry
Ensure you have insurance should a crime take place