The officers admitted that they had no suspicion of him and no reason to search him and told him he'd be arrested and handcuffed if he refused. They riffled through his books (looking for terrorist words?) and went through his bag.
BoingBoing's comment was: Welcome to Britain: now spread 'em.
The victim was carrying a videocamera and had the presence of mind (and the nerve) to record the encounter. His video is here; most people will find it both alarming and depressing. However, his name was Terence Eden and he doesn't look or sound remotely foreign, so it is good to reflect that this was a truly random search and there was no element of racism or xenophobia involved, though I suppose they might have disliked his hair style.
Thanks to Grumio for the link.