Section 14 can only limit numbers, duration and location for an assembly - it would appear they are trying to limit the protest to no more than 50 people and it's estimated there will be approx. 500 police there on the day. Officially they cannot use it to impose other conditions such as stopping you using whistles, megaphones, giving out leaflets. Nor can they use it to against processions which come under section 12.

Section 14 also does not apply in areas other than the ones specificially designated. Also it is a defense if you did not know about it, for example there was too much noise to hear the police megaphones or you did not take the paper they hand out at protest sites.

The same section was used to try and control the protests at the G8 ministerial meetings in Derby, back in March. The policing was totally over the top and protestors were only allowed to assemble between 10am and 3pm in the Market Square. According to the local rag there were "A thousand officers from 23 forces" and "policing the event was expected to cost between £1m and £2m", since there were perhaps 100 protestors it cost around £20,000 per protestor...