What else do you need? It's one of at least three prototype cars made by AC as a feasiblity study for a new "town car" in the early 1970s. All were built around the 493cc Steyr-Puch flat-twin engine that AC were using at the time in the Model 70 Invalid Carriage.
Yes, that's what it is.
It was captioned Prototype No. 3, No.2 being the same but with only 3 wheels.
This is in fact a re-post and it was said to be an AC-Reliant prototype before, with the Model 70 name being attached to Reliant. I have not been able to find anything out about Reliant's involvement in this, and of course the Model 70 was AC's Invacar. I understood this project was to replace the AC Petite, but since it dates from the 1970s I don't really think that's right.
I'll have to merge the puzzle but in the meantime here are pictures of this car along with its 3-wheeled sister-car. The AC badging can be clearly seen on the front of the car.