UKIP compiling list of people at protests against them?

So my friend was at an anti UKIP (anti-immigration/anti-gay rights party in the UK) protest the other day and said that there was someone there taking pictures of all the protestors. The person said they were from the BBC, but I know some people at the BBC and there are no plans to make a doc about UKIP or anything. Also the person couldn't provide any ID/just seemed a bit suspicious.

The other thing that makes it seem like they were trying to identify protestors was the fact that the UKIP candidates had small hand cameras on them and they were filming everything by hand, directly pointing the camera at the protestors.

I was just wondering if anyone new anything my friend could do to find out whether they had been photographed or try and stop them from making a list of people who protest against them? (apart from obviously just showing up there without a mask or anything). Just seemed similar to what the Church of Scientology did back in the day.

TL;DR any way to find out if my friend has been photographed at a protest by UKIP and stop them from IDing protestors?

Thanks a lot in advance.