President Bashar al-Assad has launched a furious attack on Britain, America and their allies, accusing them of deliberately prolonging the civil war in Syria.

Dismissing Theresa May as a colonialist and a liar, the Syrian leader claims Britain even helped stage April’s notorious chemical attack in the suburb of Douma and that its actions are giving support to the Islamic State terror group.

Today, in a rare and defiant interview, a man widely regarded as a pariah for his repressive regime – and widespread accusations that he has used chemical weapons – refuses to accept an iota of blame.

Instead, he places responsibility for the duration of the seven-year conflict squarely at the feet of Britain and America. Western powers, he says, should get out of Syria and allow the bloodshed to end.

Assad is in an outspoken mood – and believes he has good reason to be confident. Today, for the first time in six years, his forces are in full control of the Syrian capital while, thanks to the support of Russian and Iranian allies, rebel fighters and IS are firmly in retreat.

Defiant: Bashar al-Assad talks to journalist Hala Jaber in his palace in Damascus last week

‘I have always said that in less than a year we can solve this conflict, it’s not complicated,’ he tells me. ‘What has made it complicated is the external interference. The more we advance, the more support terrorists have from the West.

‘So, we think the more advances we make politically and militarily, the more that the West, especially the US, UK, and France, will try to prolong it and make the solution farther from the Syrians.’

Today – in his first interview with a British journalist since 2015 – we meet not in the main presidential palace but in a sitting room at the smaller Al-Muhajireen Palace, a relatively modest building in the heart of Damascus. Assad often works here and lives nearby.

Half a million Syrians have been killed since the conflict began in 2011, while 11 million have been forced from their homes in a country whose population stood at 23 million when the conflict began.

Silence has finally replaced the distant thuds of bombing and the roar of fighter jets above Damascus’s suburbs.

Yet Assad’s success on the battlefield has done nothing to repair his standing in the West – not merely as an autocrat, with hundreds of Syrians killed and tortured, but as a man resorting to war crimes to cement his grasp on power. Is his pariah reputation justified?

Assad, in the same measured replies, claims that the support for him proves otherwise. ‘The story you’re talking about [is] that this is a bad president; he’s killing his own people, and the world is against him,’ he says. ‘But he’s been in his position for seven years while he’s fighting everyone in this world. Can you convince your readers of this? It’s not logical. It’s not realistic. This president is in his position because he has the support of his own people.

‘We are fighting the terrorists and those terrorists are supported by the British Government, the French government, the American and their puppets.’

It is certainly quite a change for a man who was once embraced by the world as a young cosmopolitan leader when, at the age of 34, he became president.

The latest atrocity levelled against the Syrians was a suspected chemical attack on April 7 in Douma, the last rebel-held town in the eastern Ghouta region.

According to reports from the White Helmets, a controversial voluntary organisation, and rebels from Jaish al-Islam, a coalition of Islamist fighters, the Syrian military dropped bombs containing chlorine from helicopters. The reports suggested that as many as 42 were killed with scores of further casualties. Such claims were supported by videos uploaded by the White Helmets, which operate in rebel-controlled Syria, showing images of young children, allegedly choking, being hosed down with water.

Yet according to Assad it is all a pure hoax, a deliberate piece of fake news staged by Britain, France and America in order to justify the later airstrikes. ‘The UK publicly supported the White Helmets that are a branch of Al Qaeda,’ he says.

‘We consider the White Helmets to be a PR stunt by the UK. So yes, definitely, it was staged by these three countries together and the UK is involved.’

Today he insists no such attack took place, and claims this is supported by the evidence of Western journalists who visited the area and Syria’s own intelligence information. ‘It was a lie. After we liberated that area our information confirmed the attack did not take place,’ he adds. ‘The British Government should prove with evidence that the attack happened, and then they should prove who is responsible. This did not happen.’

Britain, America and their allies, in reply, say the authenticity of information on the alleged attack is unassailable.

Following the episode, the US, Britain and France launched airstrikes against Syrian research, storage and military targets to punish Assad for ‘persistent violations’ of international law.

Not, says Assad, that Theresa May is in any position to lecture other world leaders. ‘Britain and the US attacked Iraq illegally in 2003,’ he insists. ‘[They] killed millions, caused mass destruction, let alone the number of widows and amputees.’

Indeed, he provocatively accuses the UK of invading his own country in the manner of a 19th-century great power – in contrast with the Russian and Iranians who, he points out, were invited in.

‘This is colonial policy, that’s how we see it, and this is not new. They have never changed this policy... that existed in the beginning of the 20th century,’ he says.

‘For the US, the UK and France [their presence in Syria] is illegal. It is an invasion, they are breaching the sovereignty of Syria. They don’t accept anyone who has a different point of view.

‘The past five years have proved that I was right. Look at the terrorism spreading all over the world because the chaos that is supported by the West in Syria.

‘Syria is very independent in its political positions. We work for our national interests, we’re not a puppet state.’

At first, Britain’s intervention against IS in Syria was limited to air strikes. They continue, but the mission has expanded into both training and supporting local allied troops, the Syrian Democratic Forces, which are based in the country’s north and north-east.

British Special Forces are known to be on the ground in Syria. In March the Ministry of Defence announced its first fatality in the fight against IS – a special forces soldier killed by an IED.

I press Assad again on Syria’s own responsibility for the conflict. ‘This is a Syrian issue,’ he says angrily. ‘We don’t discuss it with the West. It’s not the role of the West to tell us who’s responsible in Syria, the president or the government or the army or terrorists. The West is not in a position to tell us, at the end. It interfered in a sovereign country and is responsible [for] the killing, regardless of its lies.

‘The West supported the war from the very beginning and it supported the terrorists. The West is responsible first of all.’

Assad’s isolation from Britain is all the more pointed as he spent time here in the 1990s, living in London and training as an ophthalmologist at the Western Eye Hospital. London is also the city where his wife Asma was born and grew up, the daughter of Syrian parents.

He admits missing the city, but remains guarded. ‘I lived in London, I learned as a doctor,’ he reflects.

‘It’s impossible for you to live in a city and you don’t feel there is a special link with that city or with the people you work with.

‘But you live sometimes in contradiction; that the same city that you like is the same country that’s been attacking your country, which is not good.’

How, I ask, would he like to be remembered in history?

‘It depends on which history,’ he replies. ‘The Western history? It’s going to be skewed; it’s going to tell lies and lies and lies.

‘Our history, which I care about, I hope will remember me as somebody who fought the terrorists to save his country, and that was my duty as president.’

Iran and Russia, of course, have taken much the same view, and it is their support which has turned the tide of the war in his favour.

Both countries have been heavily criticised for their behaviour at home and abroad, but Assad is unrepentant, insisting that, unlike Britain, they are upholding international law through their presence.

‘Their politics, their behaviours, their values are not about interfering or dictating; they don’t.’

With the help of his allies, Assad has set his sights on regaining the areas of the country that remain outside his control – and retaking Syria as a whole.

It remains a formidable task, not least because the Syrian Democratic Forces, a large Kurdish militia group in north-east Syria, is backed by the US.

There are currently around 2,000 American troops in Syria providing training, arms and air support to the Kurdish militia and it is clear that the SDF, which holds the largest area of Syrian territory outside government control, remains the largest obstacle.

Despite warnings from the Pentagon, Assad says that he is willing to use force against them if necessary.