Because the floors are concrete it sounds like 1960-70 construction but that isn't definite. If the floors are concrete the floor is constructed using truscons(the spelling might be wrong because they are a brand name). Truscons are reinforced concrete beams which are infilled with clinker block between each one. The partitions separating each room are built on the beams and are not load bearing. I am almost 100% certain that the walls to the cupboard can be taken down because they were built after the main construction of the flats was completed. If it is possible to measure the thickness of the wall and it is less than 4in thick just knock it down because anything less is not load bearing.

If the flats above and below have the same floor plan the wall is probably load bearing.

if this is a uk question ..it should be its meant to be a uk site ..and as you say concrete floors then almost certainly the cupboard wont be loadbearing ..and not all the flats will have same layout ..and we did not use clinker blocks in floors ..not good enough for uk

I know it would probably be best to have a structural engineer come in and give me their opinion however i would like anyones who feels they have some knowledge. I live in a set of flats. They are four flats high. Basically there is an old cupboard sort of like a pantry in the kitchen and if possible i would like to knock this down as the kitchen is very narrow and this would open it up greatly. What is the best way to tell if it is a load bearing wall ? My research suggests original plans are almost impossible to get. All i know is that both the kitchen floor and kitchen ceiling in all the flats are concrete. If this makes any difference. Thanks to anyone who takes the time to read/answer my question