Using a deer antler for a rappel anchor...PLEASE!!!
Given the "insurance" and "safety" excuses when he was caught rebuilding a Lego raft and secretly wearing a PFD, I suspect there was a real anchor hidden just beyond camera view. Alternatively, camera tricks can make all sorts of things possible. I would need a James Randi/Uri Geller type investigation before believing a thing.
"Bear Grylls and the crew receive support when they are in potentially life-threatening situations, as required by health and safety regulations."
"The programme explicitly does not claim that presenter Bear Grylls' experience is one of unaided solo survival. For example, he often directly addresses the production team, including the cameraman, making it clear he is receiving an element of back-up."