In February David Cameron wrote a message in a book of condolences at Amritsar. The massacre of hundreds of protesters at the hands of British troops in 1919, he wrote, was "a deeply shameful event in British history". "In remembering," said the prime minister, "we must ensure that the United Kingdom stands up for the right to peaceful protest anywhere in the world."

On 9 December 2010, a 15,000-20,000 strong march, much like that of Amritsar headed from the University of London Union towards Parliament Square. This was the fourth march against education cuts and the volte face on tuition fees. The vast majority were students and staff in higher education; one of them was Alfie Meadows, a Middlesex philosophy student whose course had been recently cut.

The vote in parliament was due to take place at approximately 5.30pm. Alfie waited along with thousands of others. Just before 6.11pm he suffered a massive head injury from which he nearly died. He was subsequently charged with violent disorder. Last Friday, he was acquitted along with his co-defendant, Zac King, by a jury at Woolwich crown court in London. Three other codefendants had also been acquitted at an earlier hearing. Meadows's case was always that he had been struck by a baton, and this was conceded by the prosecution during this trial.

In the light of his Amritsar observations, Cameron would do well to take stock of this case, as well as the death of Ian Tomlinson, a newspaper vendor, at the hands of the police in 2009 at the time of a different protest.

Legitimate and peaceful mass demonstration is being policed off the streets. Increasingly, heavy-handed tactics are being employed along with the potentially dangerous practice of "kettling" or corralling. It is part of a general policy by successive authoritarian governments. They brook no opposition and contrive a compliant society upon which they can wreak havoc with their elitist economic policies. Recent revelations about the activities of undercover police within the environmental movement over many years provide abundant support for this contention.

On this particular demonstration there was a discernible escalation of force deployed by police, which was not commensurate or proportionate to some small pockets of hostile reaction within the crowd. This was amply captured by police cameras as well as film taken by bystanders. It began by police donning riot gear – most notably the so called Nato helmets – together with shields. Some of these officers, including medics, chose to use their shields and truncheons offensively against protesters pressed up against them.

Later, mounted units were deployed to charge into tightly packed crowds on one side of Parliament Square. Some of this was witnessed by a doctor who had voluntarily attended the march in order to render first aid. Many of those she helped were suffering from head injuries. There was even a request from a bronze-level officer to employ rubber bullets. The silver commander in evidence accepted that this was always a possibility and had been discussed prior to the march but was not part of the plan on this occasion.

The most draconian measure was the imposition of containment (kettling) at 3.23pm, which continued for over six hours. There was scant information for demonstrators about the reasons, the duration, and the exit possibilities. Needless to say the provision of ordinary facilities were equally scarce. It is hardly surprising that tempers became frayed and led to more force being engaged.

The whole police approach to this day was ultimately encapsulated in a quite terrifying kettle on Westminster Bridge that lasted an hour and a half. Between 3,000 and 4,000 demonstrators had been herded and contained with barely room to breathe in freezing conditions, with the added risk of being pushed over the parapet into the river. Among those on the bridge was Zak King.

The overwhelming majority of these young people were responsible individuals who cared enough about fundamental values to make their voices heard. In the immediate aftermath of the student protests, the House of Commons joint committee on human rights investigated these events and reported in May 2011. They were concerned about the conditions under which kettling was imposed, but more poignantly they "were surprised to find there appears to be no specific guidance setting out the circumstances in which the use of the baton against the head might be justifiable".

The UN special rapporteur on rights to freedom of peaceful assembly and of association was more strident in his critique of the UK in January. He took account of the decision of the European court of human rights (containment does not equate with imprisonment) but condemned the practice for its "powerful chilling effect on the exercise of freedom of assembly".

We have been here before. Corralling, shields, batons, and horses were all used indiscriminately against the demonstrating miners at Orgreave in 1984. Like Meadows and King, they too were charged – and like them they were acquitted. It is time the implications of such verdicts are recognised and respected.

Chapter 3 of the coalition agreement stated in clear and unequivocal terms: "We will restore rights to non-violent protest." We are waiting.

• This article was amended on 11 March 2013 to correct the date of Ian Tomlinson's death to 2009. It originally said he died in 2011.