For individuals, there were limits (not an outright ban) from 1966 on
holding common gold coins. Earlier (post 1945), the government
controls were on the principal firms in the City who dealt in gold and
"fixed" the daily price. I have the book I need, but can't get to it
until later tonight. When this went away, I don't know off the top of
my head, but it was likely after Harold Wilson left the premiership
for the second time.
oly