Thanks SACO for your email! I just replied.
After reading the article I believe it's a project which name cannot tracked anymore.
In my book "Griffin" refers only to the company's badge and is not the name of this concept.
Further I think it was made under the lead of David Jones but was probably penned by someone of his staff — also hard to tell today.
The HAS code on the plate indicates a Vauxhall Viva base and the year is most likely 1965.