Mystery Mini derivative (80)

Mystery Mini derivative number 80 (!) comes from regular contributor Scott Barrett and it's as mysterious as can be. He wrote: Hi Jeroen, Somebody with better eyesight than me has put the registration number (CRE 263K) of this unusual buggy-type car into the DVLA computer, and it says it is a 1971 998cc Austin, so quite possibly Mini-based. Any ideas? Best, Scott" 

I have no idea whatsoever but certainly do like the looks of this creature. The picture was made by Klaus Hiltscher at London's Piccadilly Circus in 1976 and Klaus was kind enough to share it online. I have also zoomed in on the car and brightened it up a little on the computer and I do believe the registration is indeed 'CRE 263K'. Who knows more?

A bright and sunny day at Piccadilly Circus in 1976. But what's that car?

Picture Klaus Hiltscher

It seems to be registered CRE 263K, which is allocated to a 998cc Austin of 1971...

Picture Klaus Hiltscher