Cheltenham Architecture

Just had a wee stroll this evening to try to cool down a bit. Not much of a breeze so it didn't really work. I never tire of looking at the beautiful buildings in Cheltenham though. Here we have a gothic Victorian "Gentleman's residence" on the left and the Georgian terrace on the right I previously blipped in more detail on 24th June.
In this shot you can see that the final section of the Georgian terrace is detached from the rest of the building. It is joined only by an arch at ground level (not visible in shot). Does anyone know why a building would be designed this way? If there are any students of architecture out there who know the answer please let me know.