There’s something very nostalgic about Celtic Manor. Located a few minutes down the M4 from Newport town centre, it manages to feel entirely remote, an imposing stone building nestled within some 2,000 acres of grounds. Opened in 1982 by Welsh tech tycoon Sir Terry Matthews, once the richest man in the country, there’s something about Celtic Manor that brings to mind childhood holidays, from the smell of chlorine drifting from the vast pool and …