If I've understood correctly, your dash top full VIN is 124379N651234, but both the hidden (partial) VINs are the same, being 9N527946.
That being the case, and without a firewall trim tag to determine car's build date, it looks like there are several scenarios:
1) A previous owner replaced the entire upper dash, including the VIN plate from donor Norwood-built car whose VIN was 124379N651234, which ended up on car that was built as 12xx79N527946. This is unlikely, as the donor car's VIN would then be visible on the original car and would not match the original VIN on the title, and would cause issues with state DMV and law enforcement, among others.
2) A previous owner replaced the firewall and cowl area of car with VIN 124379N651234 with same panels from a donor car with partial VIN 9N527946, but retained the upper dash and original full VIN. IMHO, less likely than scenario 1 above.
3) Car was originally 12xx79N527946, but has had the VIN from a later car swapped to hide it's identity. Could also explain why the cowl trim tag is missing, as the VIN would not match the build date by a long shot. If so, the car could have been stolen and another VIN (from a wreck, rusted out body, interstate-tagged car or ?) added.
There could also be other scenarios that I haven't thought of, all sorts of things happened over the years and as your car is a race car and (presumably) hasn't been registered for a long time, who knows?
It may open up a whole can of worms, but searching one of the free official US VIN check websites for any combination of full VIN that the partial VIN could have been (*) might tell you if the car is/was once stolen, but......
(*) As it's just a partial VIN, it could have been from an L-6, V8, coupe or convertible Camaro, so the possible combinations of VIN would be:
BTW, what part of London are you from? I spent many happy years living in the Hammersmith/Shepherd's Bush area, and met my (now) wife there.