The very idea that "authorisation" is required is the enemy of freedom and democracy. The idea of a static protest legally requiring notification or permission from the state is perverse and at odds with the very concept of dissent itself, especially since the police play a political role in stifling protest, something that anyone who has attended more than the odd demonstration can testify to. They intimidate protestors with surveillance, the threat of arrest if protestors are relcalcitrant to their arbitrary demands, physical control with pens, misusing laws in ways which they were originally never intended, and occasionally violence. Intimidation serves to make demonstration unpleasant and deter as many as possible from future attendance, reducing the public visibility and effectiveness of protest. In turn this serves to whittle down the numbers to committed protestors, making the surveillance and profiling of those they see as a 'threat' (people who are more likely to instigate social or political change) an easier job for police photographers and database administrators. Ultimately the implementation of this proposal would force protestors to act in a way detrimental to their aims or face prosecution. Meanwhile it would aid the state in acheiving and maintaining any morally dubious aims it seeks to uphold whilst underhandedly giving credence to the idea that the state defends protest as an enshrined right. The proposal gives credence to the idea that protestors are a group who need to be 'watched' with state intervention being necessary and desirable. It is fair to assume that protestors are no more likely to have a criminal record than anyone else; as such the attention protestors receive in relation to their behaviour is unparalled in any other realm of society. This serves to be a tacit smear campaign against protestors and an excuse for intimidation.
The government has long used "public protection issues" as a defence for police interference and protests and SOCPA laws stifling protest. The usual argument trotted out is that there is a "terrorist threat" to the houses of Parliament when protestors are present in high numbers and/or without a police presence. There is no evidence or logical explanation to suggest this would make an attack significantly easier or more likely especially given the already high security at the site. MPs would still receive a very high level of protection if SOCPA were repealed, it is highly unreasonable that they receive a small gain in security at such a high cost to the freedom to protest. History has proven that we are all targets of terrorism, with the public being many, many times more likely to suffer the consequences than those in power. Expecting the public to pay for a little extra protection for MPs with our hard won freedoms when many consider them to be responsible for policies placing us in the line of fire, smacks at a classist and aloof attitude.
There is not a need for the police to attend a protest. Their "proactive" approach is loaded with a hidden agenda and does more harm than good to the health of our democracy and society; a concept eminently more important than the prevention of a little public disorder which now and then is a fine thing, they need reminding who they work for once in a while.