Correct re speed record.
I was going to ask that question but thought it inappropriate but since you mentioned it.
I heard that it over shot the UK and ended up over Europe (I think Belgium)
before being able to turn around. Not sure of the truth of it though.
When confirming the year, I found this great web site.
The speed record
SR-71 Speed Run-New York to London
and photos exactly as I remember it at Farnborough.
SR71 Image Archive #1