A government and politics GCSE

Was there a government and politics GCSE at one time? It might have been called something else like British Government. There is an A Level in government and politics but there doesn't seem to be a similar GCSE.
It was the British Constitution O Level.

I have ordered a copy of the textbook by Kobrin and Scott to find out what was in the course. The most recent edition I could find was published in 1979 so it might have some stuff about the EU.