I believe it is everyone as the email was for game organisers.
The email said:
2. Covid Vaccination Requirement
· You will need: ‘Proof of double vaccination, Covid-19 antibodies or negative lateral flow test will be required to gain entry ’
· This is an Excel requirement, we have no say in it, and will be policed by them on the outer doors/gates
· Please READ and understand their requirements here
https://www.excel.london/ and suggest you check again shortly before the show on 13 November