Didn't know protecting Hyde Park was that expensive, though.
I've visited Hyde Park. I think it was a challenge because they had to house round the clock teams of security and staff. The tours there suggest Churchill spent some time visiting there as did other foreign leaders. But it was basically a round the clock operation and unlike NYC or another big city, there was no Secret Service office there, so housing and feeding and paying a full compliment of security and staff was pricey, even by the standards of those years.
I'm not begrudging the fact he was there, but thinking Trump's the first one to run up a security tab is simply not true.