Grand Prix Rejects

Can anyone please help identify this mystery machine believed to be circa 1950's F1 Grand prix Race Car that DNQ
https://youtu.be/t452wxTJtS0

Maybe a Connaught or a Cooper?

At first glance i think it's an Alta, but the angle is a bit awkward.

I've seen this posted elsewhere (probably the same OP), and I've not much to contribute beyond that it looks to me like a home-built special that started life as an Alta, probably one of the F2s that they produced in the early fifties.