Poltergeist;
What you saw was either the H for the medical helicopter, or the usual circuit heliport for days when its' not the BGP.
The normal heliport could never have coped with all the movements (far too small and tight) so the BGP heliport was just on the outside of the circuit between the Bridge and Stowe.
Chris Brown, do the same again and keep all the staff smiling and laughing the way they did this year and all will be well
VH