In article .com,
"Mathew Newton" writes:

Grateful for any advice...

Stick a large sheet of aluminium foil on the inside of the
wall with thick tape all the way around the edge, and then
move everything (cupboard, contents, etc) back into place
as it is now. After a week or two, inspect it.
There will be moisture on one side of it...
If it's on the room side, it's condensation.
If it's on the wall side, it's penetrating damp.

I would expect condensation in the situation you decribed.
What is the construction of the cupboard (fixed/movable,
rear panel or open to the wall), and what's stored in it?

--
Andrew Gabriel