A long time ago when I was around 13 years old:
My father was a Cabin Service Ofiicer on Concorde in it's very early days (late 70s).
Prior to him being on Concorde he was on 747s and occasionally I would go to work with him and we'd spend the weekend in New York.
These trips became a little more difficult when he was on Concorde, obviously, but one day he decided that a good work around was to put me on the 747 flight then take up his position on the Concorde flight. Concorde would depart second but arrive first and so he could meet me at the other end. Simples!
Given the purpose of this thread you can probably guess what happened next.
Yes, the 747 flight went tech and was cancelled (or maybe postponed, I don't remember) and so Dad was in a bit of a fix.
The then chairman of BA, lord King, happened to be on the Concorde flight and happened to ask my dad if everything was OK, to which he replied "No, my son is on the 747 flight which just got canned".
Lord King replies, "Well, put him on the Concorde!"
Now, you can imagine that in 1977 no kid got a free ride on Concorde!
I was excited, the crew were excited, the Captain came and spoke to me and asked if I'd like the jump seat for take-off. there was a tangible buzz that I clearly remember to this day.
And then the Concorde flight went tech too and we went home.
Some years later when I was an ignorant teenager and had lots of opportunity to fly on Concorde using staff travel concessions, I declined to take the opportunity until it was too late, so I never did get to go on her.
Epilogue:
In 2003 I landed back at Denham after my first X country solo, just a few months after Dad had passed away, and Concorde, on her last journey up to Scotland I believe, flew directly overhead as if to taunt me further!