I think that was a case of an operational downwind quickstop gone wrong. The classic Puma dirty trick of high Nr / backed off engines / rotor droop followed by lots of excitement and embarrassment into a boggy place.
Don't think 'GB' was handling pilot at the time; according to the version the man himself gave me it was 'MT'.
Mind you, I've not seen him (G) for over 15 years so my memory might be a little rusty. Anyone know where he is these days?