I'm a bit flaky on UK Law, but if police turned up at my door and wanted to take me to a police station to be questioned - about something I hadn't done - I would refuse.
I think under these circumstances they do arrest one as a means to take one in for questioning (suppose everyone, even the guilty, claim innocence)?. But of course they must have "reasonable grounds" for doing so, and it hinges on whatever these 'grounds' are doesn't it?.
ETA Just to add I think his name and details being obtained by the press and then published in MSM is atrocious. This man was never charged with a crime.