One training/demo exercise with SAS was to rope some of them from our Wessex onto Chelsea Barracks as part of a VIP show in 1972.
We briefed that we would come to the hover, deploy the rope, and despatch the troops. As we slowed down from forward flight and I called for the rope to be let out, the crewman said, "Too late, they've gone."
The SAS take everything seriously and play for real.