Recent protest at the COP15 summit in Copenhagen saw the arrest of hundreds of protesters, up to 900 on Saturday’s march. They were then held in wire cages set up in a warehouse on the edges of the city for up to 12 hours under legislation giving police powers to make ‘preventative arrests’. Most were then released, but those charged with offences, including very minor public order offences, were deported.

The arrest of such large numbers of people signalled a clear strategy of clamping down on potentially disorderly protest, a policy of prevention being better than cure. But while many UK protesters are shocked by the treatment, it is an approach to policing they should be used to. The Danish police have clearly learned a lot from the Met.

The Politi have simply put their own slant on the British tactics of kettling. On Saturday thousands amassed for a mass march to the Bella Centre, but the police had already decided that sections of the march would never reach their destination. Police vehicles hurtled though the crowd, supported by riot police to break up the demonstration into smaller, more controllable sections. Initially they detained everyone who would sit still for several hours on the streets. They then transferred people to specially set up cages, where people were held for up to 12 hours.

The arrest of such large numbers clearly had a marked effect on the demonstration. Set up to target the ‘black blocks’ the arrests encompassed a wide range of people, including journalists, frightened teenagers and, bizarrely, a group of Hare Krishna. The more clued up black blocks, meanwhile, evaded the arrests and set about sporadic rioting in another area of the city.

The real danger of police tactics like these, is that they have the potential to deter people from taking part in large scale protests at European summits – whether that be protests against climate change, or against the domination of the G8 or WTO. In the UK, the numbers involved in political protest dropped markedly as kettling became more commonplace - as people were simply worn down by constantly having to face hours in police cordons every time they took to the streets.

It is yet to be seen whether the kettling tactics employed at COP15 by the Danish police are used elsewhere. Mass preventative arrests are a significant move away from the crowd dispersal techniques – tear gas, baton strikes etc - more normally seen in Europe, (although such dispersal methods were also used in Copenhagen, particularly when disorder was sporadic or unexpected and the police were unable to prepare).

There will undoubtedly be legal challenge to the Danish policing, as the arrests were arbitrary and the detention disproportionate. But political activists also need to resist this particular form of police bullying from the ground up. Anyone heading for the next summit may want to bear in mind that mass containment is easy for the police to pull off when people are passive and willing to be contained. Attempting to contain a resistant crowd is a whole different ball game.