Given the increased size of the building they put up (2000 sq ft) I reckon this was subterfuge to build a new dwelling which otherwise would have been refused planning permission. The position was right on the edge of their land backing directly onto the end of a cul-de-sac.
If they had got away with this and got retrospective approval for the “Spa” then, a few years hence, they probably would have applied for conversion to a house given the robust construction. 2000 sq ft is enough for three beds with a courtyard in the U-shape. And probably £500k+.
It happens a fair amount around us in the green belt where planning permission is restricted. Someone with a few acres will apply to build a stables. The stables that go up are luxury, block work with stone wall facings and a pitched slate roof with windows, all for horses! Then three,four or five years later they will apply for outline planning permission for conversion.
They think they are fooling the thick planners, because local planning laws say that new animal barns etc in the green belt should be agricultural construction of wooden walls and corrugated steel roofs, on purpose, so they cannot be converted later. But the councils are so short of budget they will turn a blind eye if there are no complaints, in the hopes of later getting a new property attracting more council tax. And they invariably approve conversion if the building quality is good enough.
So, kudos to this local authority for refusing to collaborate with Hannah Ingram-Moore.
Though it’s possible her husband, while keeping a low profile, is putting her up to a lot of it.