Published Friday, 24 January 2014
The scene of the 1982 IRA bomb attack near London's Hyde Park. (© PA)
John Downey, 61, was arrested at Gatwick Airport in May last year.
He was charged over the car bomb left in South Carriage Drive, which killed the soldiers as they rode through the park to the changing of the guard.
The explosion also injured other members of the Royal Household Cavalry and killed seven horses as they travelled from their barracks to Buckingham Palace.
Downey appeared in the dock at the Old Bailey on Friday.
He formally entered not guilty pleas to murdering Roy Bright, Dennis Daly, Simon Tipper and Geoffrey Young, and a further charge of intending to cause an explosion likely to endanger life.
He remains on conditional bail.
© UTV News