Hi Jonathon,
The original photo must have been taken in 1966 when Automobile Engineer magazine did a comparison test of four electric cars. A Telearchs Ltd. Mini Traveller Conversion, a AEI Mini Traveller Conversion, A Scottish Aviation Ltd. Scamp and the Peel Trident Electric Saloon Scooter.
Yes, the 4-wheeled Trident that nobody seems to know where it is. The 'fat P50' is in fact the Scamp. I have a four page photocopy from the magazine showin details of the vehicles.
Rob.