The liberation of the last of the so-called Islamic State’s territory in Syria has been hailed by British politicians as a historic achievement, but they warned the threat from the terror group remains.

Prime Minister Theresa May praised the “extraordinary courage” of the UK armed forces and their allies.

And Foreign Secretary Jeremy Hunt vowed Britain will “remain resolute” in its commitment against the group, also known as Daesh, and its “poisonous ideology”.

Major General Chris Ghika, Deputy Commander of the Global Coalition’s joint task force, said the terror organisation is by no means “leaderless or rudderless”, despite its loss of physical territory.

But he said he could not predict whether the fall of the physical territory would substantially increase or decrease the terror risk to the UK.

The capture of Baghouz is a milestone in the four-year campaign to defeat the group’s so-called “caliphate” that once covered a vast territory straddling both Syria and Iraq.

It was announced on Saturday by Mustafa Bali, from the Syrian Democratic Forces, who tweeted: “Syrian Democratic Forces declare total elimination of so-called caliphate and %100 territorial defeat of Isis.

“On this unique day, we commemorate thousands of martyrs whose efforts made the victory possible. #SDFDefeatedISIS”

Mrs May tweeted: “The liberation of the last Daesh-held territory wouldn’t have been possible without the immense courage of UK military and our allies.

“We will continue to do what is necessary to protect the British people, our Allies and partners from the threat Daesh poses.”

She said the Government remained committed to “eradicating” Daesh’s “poisonous ideology”.

Foreign Secretary Jeremy Hunt wrote: “Today’s liberation of Daesh’s last territory in Syria is a historic achievement. But the fight is NOT over.

“We remain resolute in our commitment to tackle the real threat Daesh & its poisonous ideology poses to people in Iraq, Syria & around the world.”

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(PA Graphics)

Defence Secretary Gavin Williamson said it had been a long campaign to end the “misery of millions”.

He added: “Due to the tireless efforts of our service personnel, we have been able to beat them back, depriving them of territory and making sure that Britain is safer.

“But we cannot be complacent. They’ve dispersed, and they’ll continue to pose a threat to Britain, and that is why we will always remain vigilant.”

Shortly after the victory was confirmed, the Global Coalition tweeted: “History shows us that groups like Daesh don’t need territory to remain a threat. Daesh will continue to use insurgency tactics which still pose an ongoing global threat.

“The Coalition is committed to supporting the people in liberated areas in Syria and Iraq and ensuring an enduring defeat of Daesh through humanitarian support.”

The US withdrawal is already underway, with its main ally, the Kurdish-led Syrian Democratic Forces warning that leaving too soon could have dangerous repercussions and a destabilising effect on the region.

Maj Gen Ghika told reporters at a Ministry of Defence briefing ahead of Baghouz’s fall: “There are no plans to scale down the contribution to Operation Shader.”

He added: “The US have said they are going to keep a presence in northern Syria so air power will play an important part in that, and we expect the British contribution to keep going on that side.

“In Iraq exactly the same maxim applies, the British troops that are training the Iraqi security forces are going to stay and keep doing what they are doing… because Isis continues to present a threat and that threat is met largely by the Iraqi security forces.”

Maj Gen Ghika said the coalition must remain “very conscious” about the continued threat of IS and warned against allowing Syria to become a “safe haven” for the ideology.

He continued: “They are not leaderless or rudderless. One of the reasons why even after the end of the physical caliphate Isis will remain a dangerous organisation is because there are members of the organisation willing to take on the struggle.

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An RAF Tornado GR4 returning to RAF Akrotiri in Cyprus following an armed mission in support of Operation Shader (MoD/PA)

“They are less experienced, they are less capable…than the people of years ago… so the organisation is weaker but there are still people willing to take on the leadership function…and that is one of the things that we target.”

Maj Gen Ghika estimated there were a few hundred IS fighters in eastern Syria, and between 1-2,000 in Iraq.

The SDF is holding more than 1,000 foreign suspected fighters in prisons that it runs in northern Syria.

The military commander said it was a “sovereign national decision” for countries on whether take back citizens who joined IS.

He said the British Government must decide whether British forces will have a role in repatriating citizens, including children of fighters.

Asked if the threat to the UK would be removed by keeping fighters imprisoned, he said: “I don’t think it removes it, but I think it reduces the threat of people of British origin who have fought with IS returning to the UK to conduct terrorist attacks”.

Maj Gen Ghika was also asked about whether the MoD will attempt to gather evidence from the battlefield once fighting is over which could be used to prosecute British fighters.

He said: “I think that’s too early to say whether that’s going to be possible but I think if we found any individual of any nation and we were able to link them to crimes and with evidence we have then we would expect them to be prosecuted under the force of the law.”