Dave T-S

The chemical action of the leaking battery causes oxidisation of the aluminium surface inside the torch and it is very difficult to get them out - I made this mistake many years ago and learned never to use anything but leakproof alkaline batteries in future. It's the outer surface of the battery that welds itself to the inside of the torch and if it's a severe case no coke/vinegar etc treatment will work.

You need to mechanically remove the battery, and that normally involves digging it out with large screwdrivers, large wood auger bits (screw type, NOT flat ones) etc, then cleaning the residue off with sandpaper etc.

It's a long job.........