They also burnt up a good chunk of tax-payers money whilst sitting rotors running on the ground for nearly 25 minutes.
1. Perhaps this was to minimise the noise to those working on the ground, while keeping the aircraft close at hand ready to respond to short-notice tasking?
2. Perhaps sitting on the ground ready to go, but only burning fuel at ground-idle burn-rates, is cheaper to the taxpayer than having the aircraft flying orbits on station?
I don't know the answers, 'cos I'm nothing to do with the task - but these seem reasonable. What was the task?