[Twosugars]

from the OP article:

A spokesperson for the Mayor of London said: “The Mayor supports the right to peaceful protest and understands that this can take many different forms.

"His city operations team have met with the organisers and have given them permission to use Parliament Square Garden as a grounding point for the blimp.

“However the organisers will also need to receive the necessary approvals from the Metropolitan Police and National Air Traffic Service in order for it to fly.”