Massed ranks of former soldiers were joined by ex-Navy and RAF personnel for a march along the Mall to Parliament to show their anger at the injustice of targeting veterans of the Troubles while terrorists go free.
The demonstrators first marched to Buckingham Palace where they sang God Save the Queen, then to Parliament Square.
This week an elderly veteran became the sixth soldier prosecuted over the Troubles.
Known only as 'Soldier B' and now in his 70s, he is accused of the murder of a 15-year-old boy and of wounding another teenager with intent in 1972.
Yet more than 500 convicted terrorists, mostly from the IRA, were freed from prison early under the Labour government's 1998 Good Friday Agreement.
Many others were issued with official 'letters of comfort' declaring they were not being pursued for murders, bombings and other offences.
Ex-soldiers are still being pursued, however.