One possibility is trying to oraganise en masse to go down there and ask the police present to define it for us and then stand at the edge and carry out a protest. As the protest is mainly about free speech we were also thinking about having people - one at a time - go into the 'Zone of National Shame' and recite Article 19 of the Universal Declaration of Human Rights (see my user bio for the quote). As the government fully supports this declaration it would be a sign of 'support' and not 'protest' which might make a firmer legal case should any of us end up arrested.
2. If you are given a 'conditional discharge' when tried in a UK court of law do you still have a criminal record? I ask this bit because my work involves me travelling to the USA and they have a policy of not letting people with criminal records into the country. This would be tricky for me. Also, if any of my American friends could clarify the laws of entry to the US that would be appreciated.