Indeed. The Airport Byelaws are very black and white which enables the Police to act quickly. Here is just one example of the powers.

https://www.heathrow.com/company/par...athrow-byelaws

3.19 No demonstrations etc
No person shall organise or take part in any demonstration, procession or public assembly likely to
obstruct or interfere with the proper use of the Airport or obstruct or interfere with the safety of
passengers or persons using the Airport.

The problem will be how many turn up but I would be confident that there's a lot going on behind the scenes by the Police.

Peaceful and legitimate demonstrations are one thing but to disrupt everyone is just not on really and I personally think their movement and cause, the latter one being a very valid, important and current issue, will backfire on them in respect of public opinion.