hanks for the response...yes my dad still doesn't believe that we have a cavity for the same reason. But I've been into the attic and looked all the way down between the 2 skins.

I've just peered over the wall again and can see that there is a polythene lining between the soil and my wall, but i doubt this will do much to help.

yes you do have an external dpc ..its the same level as your floor ...any soil must be a minimum of two course of bricks below this ...and their plants should be clear of your wall ..not touching ..will be very surprised if you do have a cavity ..up to the 1930 circa they were solid in the main...get them to remove polythene ...that alone will cause damp ..

I've recently noticed some damp patches on our kitchen wall. Very recently our neighbour built a substantial flowerbed against the outside of the same wall which is clearly higher than our damp proof course. This seems the most likely cause but before I confront them I want to be sure.

The damp patches are small and isolated and appear about 2 foot above where the flower bed ends and not directly where the soil lies. Is there anyway of proving the cause or is this a 'no brainer'.