The scale of the chaos and panic at the heart of the police response to the Poll Tax riots of 31 March 1990 - one of the most violent protests to ever take place in Britain - is revealed for the first time in classified documents released by the Government.
Confidential police radio messages and surveillance reports show how officers made strategic mistakes, surrendered control of parts of central London and ended up calling for armed response teams when all appeared lost.
By midnight nearly 5,000 civilians and police officers had been injured and 339 people had been arrested. The final bill for damages ran into millions of pounds.
But the political cost was even greater as many believe the protests signalled the demise of Margaret Thatcher, who was forced to resign eight months later.
The documents, released yesterday under Freedom of Information laws, show the day started with police reporting a crowd of 25,000 at Kennington Park at 11am to be "peaceful and friendly". By 2pm a communiqué from Special Branch noted: "There are 150 anarchists marching under banner 'Freemasons Against Poll Tax' who are under the influence of drink/drugs and have joined rear of march."
Forty-five minutes later the reports included the first references to violence and by 3pm crowd-control barriers had been pulled down and smoke bombs were being thrown at officers.
A Metropolitan Police report sent to the Home Secretary the next day said the Deputy Assistant Commissioner of the day concluded that the peaceful intentions of 40,000 had been "thwarted by a violent element of 3,000." Later reports put the crowd at nearer 200,000.
In the criminal trials of anti-poll tax demonstrators many were acquitted when video evidence showed that some of the charges had been unsubstantiated.