British policy on Syria has been "wrong every step of the way" and made the situation worse, a former UK ambassador to the country has claimed.
Peter Ford, who was the ambassador in Damascus from 2003 to 2006, said Bashar Assad's government should be given "a little credit" for the "relatively peaceful" end to the siege in Aleppo.
He added that "there is now a Christmas tree" in the city's central square, which there would not have been "if the other side had won".
The former diplomat said the UK's policy on Syria had been mistaken from the start, saying then prime minister David Cameron should either have been prepared to commit British forces onto the battlefield or refrained from "encouraging the opposition to mount a doomed campaign which has only led to hundreds of thousands of civilians being made or killed".
"We have made the situation worse," he said.
"It was eminently foreseeable to anyone who was not intoxicated with wishful thinking. The British Foreign Office, to which I used to belong, I'm sorry to say has got Syria wrong every step of the way.
"They told us at the beginning that Assad's demise was imminent. They told us he would be gone by Christmas - they didn't tell us which Christmas so they could still be proven correct - but then they told us that the opposition was dominated by these so-called moderates, that proved not to be the case.
"Now they are telling us another big lie, that Assad can't control the rest of the country. Well, I've got news for them, he is well on the way to doing so."
The Syrian regime took full control of Aleppo on Thursday for the first time in four years after the last opposition fighters and civilians were taken out of the war-torn eastern districts in buses.
Mr Ford said Assad's forces would need to consolidate their hold on Aleppo and defend against possible counter-attacks.
"However this is a time to welcome the fact that there is now a Christmas tree in the central square of Aleppo - there wouldn't be any Christmas tree if the other side had won," he told BBC Radio 4's Today.
There has been widespread condemnation of the Assad regime, backed by Russia and Iran, over the bombardment of Aleppo but Mr Ford said similar attacks were being carried out in the fight against Islamic State in Iraq and in the conflict in Yemen without the West raising concerns.
"I think we are very selective in our indignation about the Aleppo campaign. Similar bombing is going on in Mosul and in Yemen and we give the people there a pass. We don't talk about atrocities, we don't talk about war crimes although they are indisputably being committed in both those theatres. We don't talk about genocide, holocaust.
"We will be lucky if those campaigns end with the green buses - there were no green buses in Gaza, there were no green buses after the Nato bombing in Yugoslavia. I think we need to give the (Syrian) government a little bit of credit for what has been a relatively peaceful end to this terrible period."
Pressed on the regime's attack on hospitals, Mr Ford said: "It was also a war crime to use hospitals as command centres, which is what the jihadis did. It was also a war crime to use schools to store ammunition, which is what the jihadis did."