All six policemen charged with attacking pro-hunt demonstrators have been cleared.
About 60 officers were hurt during the protest
They were accused of offences ranging from assault to GBH following the Countryside Alliance's protest outside Parliament in September 2004.
On Wednesday, Pc Kurt Schenk was the last officer to be found not guilty at Southwark Crown Court.
He was part of the Metropolitan Police's Territorial Support Group called to the 20,000-strong protest.
The other five who were either found not guilty or had the charges dismissed are Pc Neil Latteman, Pc Tim Grant, Pc Edward Cudmore, Sgt Darren Murphy and Pc Barry Jenkins.
Assistant Commissioner Tarique Ghaffur said: "These officers policed a very long and very difficult demonstration on 15 September 2004.
"They were faced with a hard core of protesters who were both determined and violent, uninterested in lawful protest and intent on breaking barriers to gain entry in to the Houses of Parliament.
"Police officers - doing what is essentially their job - were faced with a barrage of missiles that included fireworks, sections of scaffolding and barriers.
"Sixty police officers were injured that day, mainly as a result of crowd action.
"Every day police officers are required to go in to situations where bravery is not just expected, but demanded. These officers do this without question.
"Clearly there are lessons to be learnt, and we will be looking to work with the IPCC and the CPS to examine what these lessons are".
A Countryside Alliance spokeswoman said: "Something went seriously wrong with the policing in Parliament Square on 15th September 2004 but after this we are still no closer to finding out what.
"Responsibility for the problems lies clearly with government ministers. It was they who enraged thousands of ordinary people by allowing the Hunting Act on to the statute books against all logic and democratic accountability.
"The hunting community does not blame the police but it does blame the government."