Royal 308?

I was looking through some old photos the other day...(you guys make me all nostalgic and i found a pic of a white body kitted 308 GTB with large rear spoiler (sort of Koenig kit looking) with the reg "9 HRH" . I cant imagine any of our monarchy driving around in it, so was it just a smart ar5e with tickets on himself or was it a foreign royal?
It was parked just round the corner from my Fav oldbook shop Albion Scott Ltd in Kensington.