Back in the day' in 1985 (I was 15 yrs young)...I went to King Edward School in Bury St Edmunds, me and two other aviation enthusiasts were selected to spend two weeks at the Hall as 'Work Experience'. Two of us spent some time with the 'Maint' department and the other lad spent most of his two weeks up in the old tower, we just wanted to get close to the aircraft etc!....we were given a very rare opportunity to have a look around the SR71's Hanger it was then we learned that there were actually two Blackbirds stationed at the Hall!...anyway, the tour was fantastic & we were able to get close enough to touch them both and really get a tangible feel for what they were all about!.....the guy that took us around informed us that the time for the launch was always random, whether it be morning, noon or night in order to maintain it's covert reputation etc. I witnessed several launches and the most memorable was when I was in the Biology class at School some 10 miles away!.....I remember hearing a distant thundering roar, I knew exactly what it was so I turned around and searched for any sign I could in the clear blue sky. After a few seconds I could see a vapor trail starting to appear and as it did so, I could just make out the Blackbird at the front of the trail....it started to make a huge spiral shape in the sky as it ascended, it disappeared after a few turns, but what a show. It was obviously on an operational mission as it climbed so high in a short space of time.
We unfortunately missed out on a refueling mission in a KC135 & subsequent RV with the SR71 due to some 'insurance risk' .....but that's another story!
Anyway, I thought I'd share that with you....hope you don't mind!

P.S. Very nice nostalgic images 'manorbleak'....they stirred up those memories!