Many thanks to those who have contacted me about the 'moat' between Hilperton and Trowbridge.
I contacted Rights of Way at County Hall and an Highways engineer visited the site yesterday.
As a short-term 'solution' he dug a 'drainage gulley' to help draw the water level down. Long-term, WC will consider what action to take.
I have suggested a few cubic metres of road scalpings, but there might be a better solution.