The Black Buck missions achieved far more than was intended.
Bluntly put:
In terms of eliminating its primary objective - it failed.
In terms of scaring the cr@p out of the enemy and forcing them to remove their ONE trained interceptor sqdn north to protect other assets it worked, even if this was un-intended at the time.
This was all it achieved, but it was more than enough. Yes it contributed a lot to global warming, but with the Mirage 3s up north, the final outcome was made a lot easier because Sharkey Ward and Andy Auld and their teams did not have to fight them (even though the outcome would probably have been the same)
I remember the first raid as being a huge morale booster despite working 20hr days at the time.
A job very well done.