That batten uses the same base as the ceiling rose of the same make, with the lamp holder part held in place by a twist on lid, similar to the ceiling rose, but with a much larger hole in the middle.
Doesn't really show in the pic., but my problem with that particular light is the way the lamp projects horizontally into the cupboard space, where it is in serious danger of just being snapped off by stuff placed inside, or someone simply trying to reach the back corners of it. Should have been a low profile enclosed fitting of some kind.