The music lasted seconds. This was easy to judge by Reuters Square being overloaded with silver clocks on posts, some kind of modern art, stress-inducing set up that constantly makes you feel like you are late for something.

The police presence was incredibly stupid, considering the innocent piece of fun that was about to take place, and was announced very publicly on the BBC.

The only assumption to be made was the police had panicked, feared the worse case scenario and thought an anarchist army of thousands were about to descend on the financial district and burn it to the ground - not an unusual outcome to arrive at in this climate of constant fear, where yelling "look out behind you" on Tube station platforms has never been so much fun, or standing in the supermarket, looking at bags of flour and giggling.

So, large numbers of police everywhere from the moment you exited Canary Wharf Tube station, what looked like every Forward Intelligence Team in London, a wall of motor cycle cops nicely lined up (not a stress-inducing piece of modern art) and paddy wagons in every nook and cranny, especially around the HSBC building.

The arrest on the video was a young man who earlier had been spotted by FIT and taken off for a thorough search and questioning. And they found nothing on him. I was told today by a third party the reason he was given for being targeted by police was, quote, he was a "known protestor". And, he may correct me on this, but I believe that is not the first time that statement has been used as an excuse to detain and search him.

The arrest, from the video perspective, is confusing as to why the three officers decided to grab the arrestee after following him very closely, other than the police operation cost a lot of money and someone needed to be grabbed in order to make it look worth while; and the MET and City police could walk away with just one egg smashed on their faces rather than a 12-pack of free range.

One person at the scene said other people, who were on the Mayday march in Central London earlier that day were turned away by police even before they exited the Tube station.

The end of the video shows some of the crowd from the Mayday bloc leaving the beach party being followed at some distance by one of the suited undercover men. Then the final piece of film shows the remaining undercover watching the beach party.

I did catch part of the conversation by three of them, after returning from following the bloc crew's safe departure.

"Maintain a low visible presence," one said. Two left, leaving this one gent propped up smoking and watching.

But I doubt they were nothing more than bored private security enjoying the chance to play James Bond for the evening.