Relatives of the 1982 Hyde Park bomb attack have appealed to the public for support in their quest for justice.
Four members of the Royal Household Cavalry were killed as they made their way from their Kensington barracks to a Changing of the Guard ceremony Horse Guards Parade when they were fatally wounded by an IRA nail bomb, secreted in nearby car.
Suspect John Downey stood trial at the Old Bailey in 2013 for his role in the terror attack, but jurors were discharged after it was revealed he had received an assurance from former Prime Minister Tony Blair that he was no longer wanted as part of the controversial On The Runs (OTRs) scheme.
Supporters whose campaign for justice has now lasted 35 years marched from the barracks to Wellington Arch in Hyde Park on Saturday in an effort to keep their cause in the public eye as they seek the £620,000 needed to launch a civil prosecution against Mr Downey.
Mark Tipper, whose teenage brother Trooper Simon Tipper was among those killed, told the Press Association: "My brother had only been married a week, it was his first duty back after honeymoon, he was just 19 - nobody could imagine what that poor bride felt like, and 35 years on I know she (widow Louise) still hurts.
"Back then it wasn't like today - when we lose soldiers so horrifically in Iraq and Afghanistan there's a little help now, back then it was just 'get on with it and sort your lives out'.
"According to our solicitor we need to raise £620,000 - it sounds one hell of a lot of money, but not for soldiers' lives.
"I know that if our Prime Minister looked at her coffers there is special funding for cases like this, but we get no response to letters. The only people who can help us is Joe Public."
Supporters have so far raised £67,000, but say they have received no help from central government. Their ire was made more acute by revelations Mr Downey was handed £50,000 in legal aid for his defence when they were denied such help.
Mr Tipper, 57, said: "If that (OTRs) letter had not have gone to Downey that trial would have continued and he would have been found either guilty or not guilty.
"We as families were never given that chance. All we want to know is that if this man did it, he will be brought to justice."
The deadly blast on South Carriage Drive also killed Squadron Quartermaster Corporal Roy Bright, 36, Lieutenant Anthony Daly, 23, and Lance Corporal Jeffrey Young, 19. Seven horses were also killed, while many other bystanders were injured.
Mr Downey has denied involvement in their deaths.