You are going to have to back that up with a source. It sounds pathetically weak to me. The BBC did not even turn up. How would they know in advance how many are attending?
If you can find me a BBC News report on a march on a national issue that had 3,000 marchers I’ll. concede. I had a bit of a Google before posting and found nout.
Good work on finding an example from lockdown when gatherings were illegal. Clearly normal rules applied then 🤦 For context, that demo tooll place on March 21. On March 29 restrictions were relaxed to allow outdoor gatherings (including in private gardens) of either 6 people (the Rule of 6) or 2 households will also be allowed.
So yes, on March 21 2021 a gathering of several hundred people was newsworthy.