this is a breathtaking space; having originally had a flat ceiling, probably similar to the west transept and tower, the height achieved by collonade, triforium and clerestory is not intruded into by vaulting. The aisles are also 2 storey, so the triforium is lit.
The present slightly curved ceiling is from the 1860s restoration (painted by Mr. Le Strange, of Hunstanton then finished after his death by Mr. Gambier Parry, of Highnam ; it outlines the geanealogy from Adam to Jesus. It seems an odd place to do it and, to my mind does nothing for the space so I have downplayed the colour slightly...but compare it to John's where it is given full rein http://www.pbase.com/jhaydnreynolds/image/151386911
Beyond the nave you can see the light from the central octagonal lantern and through to the choir; note how there is an infill below the main arch to lower the 'ceiling' level