Most people know it as "The Old Music Library", and in its latest reincarnation as a restaurant (what else in Brighton!) the smart dark-grey paint seems to render the Brighton dolphins over the door much more discernible. It was, in fact, built in the 1920's as the showroom for the municipal gas company; those being the days when coal-gas was still manufactured and distributed locally.
For several years while the Museum complex was undergoing the millenium £10M renovation it also served as the Local History Centre. The present manifestation may be the first time the building has been out of some kind of municipal use.
Maybe not a great bit of architecture, the top "slabs" seem over ponderous, but it makes a whimsical pairing with the narrow Victorian facade next door. It is good it is finding a new use.