Methodology used to calculate crowd size for Unite The Kingdom rally

Freedom of information request reference no: 01.FOI.25.047731

I note you seek access to the following information:

How does the Met calculate crowd size?
Specifically for the UTK rally on 13 of September.
150k is the amount given by the Met,
What methodology was used to come to this figure?
Was this figure advised by an source or organization outside the MET?
If this information did come from an outside source who provided the information?

Decision

I have today decided to disclose the located information to you in full.

Please find below information pursuant to your request above.

This was calculated by utilising CCTV, officers on the ground and NPAS (National Police Air Service) alongside partners assessment by the MPS.