A Scotland Yard officer will be charged with killing Ian Tomlinson at the G20 protests after a dramatic U-turn by Britain's top prosecutor.
Relatives of Mr Tomlinson reacted with delight as the Director of Public Prosecutions said there were now realistic chances of a manslaughter prosecution against Pc Simon Harwood.
Keir Starmer QC, who last year dismissed criminal charges, changed his mind after reviewing new medical evidence and an unlawful killing verdict by an inquest jury.
Pc Harwood, a father of two from Carshalton, Surrey, will appear before City of Westminster Magistrates' Court on June 20.
Mr Tomlinson, a homeless 47-year-old newspaper seller, collapsed and died on the fringes of the demonstrations in central London on April 1 2009.
Speaking after meeting Mr Starmer today, Mr Tomlinson's stepson Paul King said relatives were "really happy" as a court summons was issued against Pc Harwood.
"We are a big step closer to where we want to be," said Mr King, flanked by Mr Tomlinson's widow. "We should have been here two years ago but we are here now and we are more than happy."
The DPP, delivering his statement at the Crown Prosecution Service's headquarters in central London, said new medical evidence at the inquest and the opinions of experts during the hearing helped change his mind.
He added: "The difficulties that would now confront any prosecution have changed in nature and scale from last year when a decision was taken not to prosecute, although it is clear that real difficulties remain.
"Taking the evidence as it now stands, we have concluded that, even with those remaining difficulties, there is now sufficient evidence to provide a realistic prospect of successfully prosecuting Pc Simon Harwood for the manslaughter of Mr Tomlinson.
"That being the case, it is clearly in the public interest that criminal proceedings be brought.
"Accordingly, a summons charging Pc Harwood with the manslaughter of Mr Tomlinson has been obtained from the City of Westminster Magistrates' Court."
Responding to the announcement, Metropolitan Police Commissioner Sir Paul Stephenson said: "This is clearly a very, very serious matter for all concerned."
He added: "I have got to be very, very concerned at an inquest verdict that returns a verdict of unlawful killing involving, as the inquest did, one of my police officers.
"My sympathies continue to be with the Tomlinson family."
The death became an international controversy after New York businessman Christopher La Jaunie handed footage he had taken of a police confrontation to the Guardian newspaper.
The DPP launched a "thorough" review after the unlawful killing verdict was returned by a jury earlier this month.
CCTV images, police helicopter footage and hand-held video recordings show Mr Tomlinson cutting a lonely figure as he staggered away from a police cordon after being hit with a baton.
Footage shows Mr Tomlinson gesturing to police and appearing angry after being sent tumbling to the ground.
Widow Julia said the death devastated her family, adding: "I remember feeling he was the best thing that ever happened to me."