I'm including this here because it is an example of misleading reporting being as much of a problem as idiots in uniform. This Daily Mail report requires careful reading:

A schoolboy was held as a terrorist suspect by police support officers - for taking photographs of a railway station on a geography field trip.
Fabian Sabbara, 15, was dressed in his school uniform when he was stopped by three police community support officers for taking photos of a station on his mobile phone.
He explained he was taking pictures, as well as pedestrian counts and a traffic survey, as part of a GCSE project.
But PCSO Barry Reeve told Fabian, from Cheam in South London, to sign forms under Section 44 of the Terrorism Act, which allows police to stop and search at random anyone they suspect of terrorism.
The pupil from Rutlish High School, Merton, was forced to comply or face arrest after he was stopped at nearby Wimbledon railway station.

More at Mail Online 

It's worth notiing that PCSO's have no powers to search, detain or arrest under s.44 of the Terrorism Act. They can ask questions, but search can only be conducted in the presence and with the supervsion of a police officer. They have no power to detain or arrest except citizen's arrest - which they are strongly discouraged from using because it is legally problematic and can often result in accusations of unlawful imprisonment.

The Mail piece suggests that all of the above happened. But the Mail backtracks on its inferences : 'Metropolitan Police spokesman Beverley Kassem said officers did not search him and no further action was taken'. Ah.

So from a careful reading it seems nothing more happened than a PSCO asked Sabbara who he was and what he was doing, then issued him with a S44 record of stop and search. Anyone who does not comply with s44 is liable to be arrested and Sabbara will have been told this. All perfectly correct, in other words, albeit yet another example of the futile and annoying stupidity of s44.