Worked out this afternoon if I go outside with a T shirt on it rains, put a lightweight waterproof coat on and it does not.
Cupboard under stairs tided. Had a 3 x 9 litre boxes of lightbulbs in it plus similarly sized tray of them, timer switches, surplus aerial leads and associated qbits, an elderly 10.inch TV and a long unused floor lamp plus tins of paint and somewhere behind all that the "fusebox".
TV and floorlamp (once fully disassembled as it was more scrap metal than small electrical appliance) taken to the recycling site and all the high electricity using lightbulbs (which the local charity shop said they would take) bagged in the car boot.
Down to 1 9 litre box of lightbulbs and another now full of all items bar the paint which are easily moved to access the "fuse box'.
Mystery is amongst the clutter outside of it of tins of paint that needed putting back my 1m metal rule was not hiding. Now more puzzled as to where it has gone.