Quite easily, even retrospectively. It has no impact on his neighbours, doesn't create an eyesore, etc. He had the planning folks round, had them speak to his architect. It's all legit and done the correct way.
Colin Furze - and at least for part of it he didn’t! The council sent him an enforcement notice and he had to get it done retrospectively
His underground garage however has planning permission- you can find it on the council’s planning portal
tbf all of it now has planning permission it was just retrospective, the docs are still published the same way