Foreign Secretary William Hague today welcomed the conviction of former Liberian President Charles Taylor for crimes against humanity.
Mr Hague said the verdict should serve as a warning to Syria's president Bashar al-Assad, who has been accused of human rights abuses against his own people.
The successful trial of the former Liberian leader was also hailed by former PM Tony Blair, whose decision to send UK troops into neighbouring Sierra Leone in 2000 is credited with hastening Taylor's fall from power.
The Royal Marine detachment was initially tasked with evacuating foreign nationals, but the extension of their mandate to support a UN force helped tip the military balance against the Taylor-backed RUF rebels and bring about a ceasefire to end a bloody civil war in the west African state.
Taylor himself fell from power in 2003 and was today found guilty at the UN-sponsored Special Court for Sierra Leone at The Hague of aiding and abetting war crimes and crimes against humanity by supporting the brutal rebels in return for blood diamonds.
Mr Blair told ITV News: "I think Britain as a whole can be immensely proud of what it has done for Sierra Leone and what it is doing.
"It is not often you get a situation in which the clarity is so obvious. Either you intervened or this country's democracy was given over to a murderous group of thugs and gangsters. The intervention was successful. The country has been struggling, it is still struggling but it is on its feet and is able to move forward which is a great thing."
Mr Blair added: "It is really important for Sierra Leone to have had the trial process because what people have got to understand is they engaged in this attempt to damage democracy and kill and harm people. In the course of that then, there is going to be a comeback, there's going to be a moment of accountability. So I think it is very important for people in Sierra Leone, even though primarily they are focused on their future and all the challenges, they have to draw a line under their past."
In a message on Twitter following the verdict, Mr Hague said: "Charles Taylor: justice has been done. Remember his victims, and remind Assad: there is no expiry date for crimes against the innocent."
And in a statement released later by the Foreign Office, he added: "This landmark verdict demonstrates that those who have committed the most serious of crimes can and will be held to account for their actions; it demonstrates that the reach of international law is long and not time limited and it demonstrates that heads of state cannot hide behind immunity.
"The verdict can only be a small comfort for the victims and relatives of those killed. But the Court's authoritative view of what occurred will play an important role in helping the people of Sierra Leone come to terms with the past and consolidate national reconciliation."
Taylor, who was president of Liberia from 1997-2003, pleaded not guilty to 11 counts of war crimes and crimes against humanity, including murder, rape, terror and conscripting child soldiers.
But presiding judge Richard Lussick said prosecutors in a trial which ended a year ago had proved beyond reasonable doubt that he was "criminally responsible" for aiding and abetting crimes by rebels in Sierra Leone.
Lussick said Taylor provided arms, ammunition, communications equipment and planning on a "sustained and significant" basis to rebels responsible for countless atrocities in the 1991-2002 civil war.
A sentence will be imposed later. Taylor faces faces a maximum term of life in jail, to be served in Britain. He is the first African head of state convicted by an international court.