He was released the next day, but his computers were not returned, nor was his record expunged.
Mery's "crime" was carrying a "bulky" backpack (e.g., a laptop bag), wearing an "unseasonably warm" coat (it was one of the coldest July days on record), and "avoiding the police" (he was looking at an SMS on his phone when he went through the turnstiles and so didn't make eye-contact with the officers there).
There is not one single piece of evidence to suggest that Mery is a terrorist, and yet the tools of his livelihood and all his personal data are now squirreled away in a police evidence locker -- the police haven't even given him an inventory or receipt for all the goods they stole.
This isn't an anti-terror investigation, it's a mugging. And it could happen to you. Hell, if it happened to me, I'd probably just be deported, since I'm only an immigrant, and not a citizen.
If you don't want to get mugged by the coppers whose salary you pay, write to your MP and city councillors about David's plight. I just sent a note with much of this post and some additional text to mine:
This is institutionalised theft masquerading as anti-terror investigation. It makes Londoners less safe because it deprives us of the certainty that the police are taking sensible measures to protect us against terrorism, and because it instills the fear that the copper in the tube is a mugger in waiting, who might at any moment swoop in and confiscate thousands of pounds' worth of kit and insert us into the criminal justice system.Link (Thanks, Ewan!)
Update: David sez, "I was not denied counsel. I chose not get a solicitor while at the station. This was probably a mistake (not used to be in such situations), but it was entirely my choice."