The damaging admission that a British drone was involved in the “accidental killing” of 62 Syrian soldiers has exposed the truth about how far the UK has been drawn into this bloody and unwinnable conflict. And it may also provide the Syrian president Bashar al Assad and his allies with sufficient grounds to bring war crimes charges against Britain.

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Given the recent lessons of the Chilcot inquiry into the Iraq war, it seems barely conceivable that we could be unwittingly repeating the calamitous mistakes of Iraq. Yet when parliament voted last year to approve limited military action in Syria, MPs restricted British forces to airstrikes against specified Islamic State targets.

Last weekend’s battlefield bloodshed preceded the horrifying bombing of a UN aid convoy by as yet unknown forces. The killing of Syrian soldiers has allowed Assad to turn the tables on the coalition and accuse Britain and America of deliberately targeting his forces. It is an accusation that once again places Britain at risk of fighting an illegal war in the Middle East.

Assad claims the attack on his troops could not have been a mistake. Syria’s Russian allies sought an emergency meeting of the United Nations security council to review the incident.

And Russia’s UN ambassador, Vitaly Churkin, described the timing of the attack as “highly suspicious”, adding that it did not look like an honest mistake. It was even claimed that Isis forces, the intended target of the coalition airstrike, used the attack to take ground from the regime forces.

The Ministry of Defence has denied that Syrian soldiers were deliberately targeted and said the incident would be fully investigated. But should the Syrian victims want to take a case to the international criminal court in The Hague it will be doubly embarrassing for Britain. The US is not a signatory to the ICC treaty, so it would be left to Britain, Washington’s junior partner in the coalition, to defend any charges. The Hague, of course, is exactly where many wish to see Assad (who also hasn’t signed the ICC Treaty) facing charges of war crimes. This week foreign secretary Boris Johnson and human rights barrister Amal Clooney stepped up their own efforts to gather evidence against all those accused of committing atrocities in Syria – including Assad’s forces.

Among the 223 MPs who voted against taking military action last year many will have known that Syria was not like any other conflict, and British forces risked becoming caught up in a confusing and dangerous civil war.

Those who did vote for airstrikes thought they had done enough to restrict military action to the limited terms of the motion, which named Isis as the sole enemy. During the debate leading up to the December vote, David Cameron told the Commons that he was only asking to end the absurdity that prevented British aircraft from chasing Isis terrorists into Syria from Iraq.

He said the targets were to be “the leaders of this death cult itself, the training camps, the communications hubs and those … plotting against us”.

Figures this month from the MoD show that since December, the RAF has flown a thousand sorties over Syria, striking targets 79 times. Typhoon and Tornado jets, supported by Raytheon Sentinel R1 ground surveillance aircraft, have dropped more than 100 giant Paveway bombs and 23 Brimstone missiles. Scores of special forces based in Jordan and Iraq have taken on Isis forces and killed dozens of fighters on the ground.

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But it is the deployment of the RAF’s fleet of 10 Reaper drones that may have sucked British forces into unauthorised conflict. It was a British Reaper that took part in the US-led operation that caused the “accidental” deaths of the 62 Syrian soldiers and threatened the fragile truce.

And it is the use of Reapers, based in Iraq, and flown remotely by satellite from an RAF base in Waddington, Lincolnshire, against Isis fighters who are British citizens that has triggered an inquiry. The government has confirmed that Reapers took part in operations to assassinate British Isis fighters in Syria who are said to have posed a direct threat to the UK. One of these strikes took place before the Commons had voted in December in favour of limited military action in Syria, killing Reyaad Khan, 21, an Isis fighter from Cardiff who had appeared in a terrorist recruitment video. He died as a result of a joint US/UK operation in August last year along with Ruhul Amin, 26, from Aberdeen, a passenger in the car in which they were travelling. Further joint US-UK operations took out cyber-terrorist Junaid Hussain, 21, also in August, and Isis executioner Mohammed Emwazi, 26, also known as Jihadi John, in November.

Those deaths are now being investigated by a joint parliamentary committee on human rights, which has already said that the use of drones in the government’s “targeted killing” programme left British pilots and commanders operating them vulnerable to murder charges.

It found that confusion over the precise legal justification exposes frontline personnel and all those involved in decisions to launch lethal attacks outside warzones to “criminal prosecution for murder or complicity in murder”.

Calls for the government to publish the legal advice that supports its claim that Britain is acting in self-defence have so far been rejected. Even if it publishes a full response to the human rights committee report ministers are unlikely to concede any ground to those who believe UK military action in Syria may have broken international law. But as each month passes Britain becomes more and more embroiled in the Syrian quagmire. As we commit increasing numbers of personnel and more hardware to US-led military operations, the risk of being caught up in illegal acts will only increase.