The free-to-enter event, to be held in the City of London, comes amid concerns that photographers will be targeted by authorities in the run-up to the London 2012 Olympics, as part of heightened security operations.

Several incidents in recent weeks have again turned the spotlight on the conduct of private security guards.

‘Local authorities are selling off record amounts of parks, playing fields and allotments to the private sector,’ say organisers who question ‘this tight control of the public realm’ and its affect on ‘freedom of expression’.

Defence of the Public Realm will take place at The Great Hall, Bishopsgate Institute, 230 Bishopsgate, London EC2M 4QH.

The event starts at 6pm and will be chaired by architectural photographer and campaigner Grant Smith.

Speakers include Andrew Altman, chief executive of the Olympic Park Legacy Company and documentary photographer Marc Vallée.

Along with Grant Smith, Vallée helped set up the campaign group, I’m a Photographer Not a Terrorist.

The line-up is also due to feature writer and journalist Anna Minton, author of Ground Control.

Last month, City of London Police repeated warnings that private security guards have no right to stop people taking photographs.

The City of London Business & Community Bulletin, sent to thousands of people in May, stated: ‘The vast majority of people taking photographs are doing so for entirely innocent purposes, and the fact that someone is taking photographs does not in itself indicate hostile reconnaissance or other suspicious behaviour.’

For full details of the event click HERE