Bashar al-Assad’s family’s 50 year rule of Syria is at an end with the president fleeing to Russia on Sunday after rebels took over the capital Damascus.
Prime minister Sir Keir Starmer has said the UK will play a part in “ensuring a political solution prevails” while welcoming an end to the “barbaric” regime.
The Syrian army reportedly notified officers on Sunday that Mr Assad’s regime had ended, though the army later insisted it was carrying out operations against “terrorist groups” in the key cities of Hama and Homs.
Mr Assad has reportedly been granted asylum in Moscow, his long-time ally and protector, and is now working to ensure a “peaceful transfer of power,” according to Russian media.
His exact whereabouts is still uncertain, although a Syrian Air plane took off from Damascus airport around the time the capital was reported to have been taken by rebels.
Having ruled over Syria with an iron fist for two decades, Mr Assad’s departure has been greeted with jubilation on the streets of Damascus with thousands celebrating his fall.
The path to peace could be rocky, however, with the leading insurgents in Syria being Hayat Tahrir al-Sham (HTS), an Islamist rebel group which is banned in the UK.
Sir Keir urged all sides to protect civilians and ensure aid could reach the vulnerable as he responded to the overthrow of the Syrian regime.
He said: “The developments in Syria in recent hours and days are unprecedented, and we are speaking to our partners in the region and monitoring the situation closely.
"The Syrian people have suffered under Assad's barbaric regime for too long and we welcome his departure.
"Our focus is now on ensuring a political solution prevails, and peace and stability is restored.
"We call on all sides to protect civilians and minorities, and ensure essential aid can reach the most vulnerable in the coming hours and days."
It marks a turning point for Syria, shattered by more than 13 years of war which has turned cities to rubble, killed hundreds of thousands of people, and forced millions abroad as refugees.
Mr Assad’s fall marks the end of a brutal 50-year family dynasty, but the rebellion has also raised fears of fresh instability in the Middle East.
HTS is being treated as an alternative name for Al Qaeda, the group once led by Osama bin Laden, according to the Government's list of proscribed organisations.
Asked whether he would deal with the group, Sir Keir told broadcasters in Abu Dhabi: "It's very early days at the moment.”
Ex-head of MI6 Sir John Sawers said HTS was thought of as "too close to Al Qaeda" when he was in post, but added that its leader Mohammed al-Golani had "made great efforts over the last 10 years to distance himself from those terrorist groups".
Meanwhile, US President Joe Biden and his team were monitoring the "extraordinary events in Syria" and were in touch with regional partners, the White House said.
"We celebrate with the Syrian people the news of freeing our prisoners and releasing their chains and announcing the end of the era of injustice in Sednaya prison," the rebels said, referring to a large military prison on the outskirts of Damascus where the Syrian government detained thousands.
Thousands in cars and on foot congregated at a main square in Damascus waving and chanting "Freedom" from a half century of Assad family rule, witnesses said.
As Syrians expressed joy, Prime Minister Mohammad Ghazi al-Jalali said the country should have free elections so Syrians can choose who they want.
Mr Jalali also said he had been in contact with rebel commander Abu Mohammed al-Golani to discuss managing the current transitional period, marking a notable development in efforts to shape Syria's political future.
