A man has been charged with the murders of four soldiers in the IRA's 1982 Hyde Park bombing, Scotland Yard said.
John Anthony Downey, 61, of County Donegal, Ireland, is accused of being responsible for a car bomb left in South Carriage Drive.
The explosion killed four members of the Royal Household Cavalry as they travelled from their barracks to Buckingham Palace.
He was arrested at Gatwick Airport on Sunday.
Sue Hemming, head of special crime and counter-terrorism at the Crown Prosecution Service, said: "The Metropolitan Police Service has been investigating the explosion near Hyde Park in London which occurred on July 20, 1982. We have reviewed the evidence gathered and authorised them to charge John Anthony Downey, 61, of County Donegal, Ireland.
"It is alleged that Downey is responsible for the improvised explosive device contained in a car parked in South Carriage Drive, SW1, London, which resulted in the deaths of four members of the Royal Household Cavalry, Blues and Royals, as they travelled on their daily route from their barracks to Buckingham Palace.
"Downey has been charged with the murders of Roy John Bright, Dennis Richard Anthony Daly, Simon Andrew Tipper and Geoffrey Vernon Young. He has also been charged with intending to cause an explosion likely to endanger life contrary to S3 Explosive Substances Act 1883."
Downey will appear at Westminster Magistrates' Court on Wednesday afternoon.
The Hyde Park bomb came just over a year after IRA hunger striker Bobby Sands died in the Maze Prison. The Household Cavalrymen of the Blues and Royals were riding through Hyde Park on their way to the Changing of the Guard when a bomb cut through their ranks. Four men and seven horses were killed and a number of police officers and civilians were injured.
Less than two hours later, a second explosion in a Regent's Park bandstand killed seven Royal Green Jackets bandsmen. The allegations against Downey are not related to this second incident.