This is a tip to all drivers of double decker busses. 12 inches is too low! However on the event of going under such a bridge you will end up with quite a nice convertible double decker bus (or a tour bus if in summer).
Also the police in Southampton are very slow to respond to said incidents allowing students from the local Halls of Residence to stand, watch, point. laugh and take lots of photos.
UPDATE: Photos taken by a fellow Roke summer placement student and staying in the same halls can be found HERE
12″? Definitely too low. Do you mean 12′?