Supporting beam?

[feebal]

I live in a two up, two down terrace. The stairs go up the middle of the house. Each of the two bedrooms have a small alcove which basically uses up dead space above the stairs. These alcoves are of no use individually as they're too small to do much with. I've boarded up the alcove in one bedroom and have knocked through from the other alcove to create one bedroom with no alcove and one with a bigger more useful storage space (with me so far!).

The problem I've got is that when I knocked through there was a wooden beam running vertically between the alcoves (lath and plaster walls). As this is only about a foot (if that) from the party wall is it likely to be supporting anything? I'm guessing it's more likely there to aid the original construction of the walls...

I've got someone going up in the loft to see where it goes but would appreciate suggestions in the meantime. Thanks.