This is what happens when you you film the Gurkin in London.
http://www.guardian.co.uk/uk/2009/dec/11/snapshot-special-branch-terror-suspect
Apparently you are allowed to film the top but not the bottom. If security flagged you as suspicious, the police have the right (and quite rightly so) to question what you're doing.
I kinda side the plain clothes police who was only there doing his job but to be honest, the other 2 uniformed officer just jumped in straight waving the Section 44 flag.
I know the reporter was being abit of a PITA with his rights, which is within his rights to not reveal his name and details nor show the officers what he had filmed UNLESS the police offers have very strong evidence of the suspect being involved in terrorism / gathering intelligence in the name of.
It wasn't until the police officers bring up the obstruction of police officer issue, the reporter had no choice but to give up.
The next report by the guardian again
http://www.guardian.co.uk/uk/2009/dec/15/italian-student-police-arrest-filming
This I think is WAY OTT compared to the previous. Apparently being foreign and different in tone due to the language barrier amounts to being cocky by a PCSO, whom later flagged up something unrelated to the filming (that the student was cycling on the wrong direction earlier, in which she apologised) only to later be subject to an open arrest, with her pinned to the ground, jailed and forced to sign an £80 fine.
The first vid, I am semi on the fence but the second one is just stupid, more on the PCSO part. And with regards to the cocky tone, I felt it more from the PCSO than the student (who tbh, sounds like a drunk speaker - but I know of Europeans speaking like that as they are translating in their mind before they speak, much like how an English speak to a French, in French.)