Although these elements are thought to include American and British special forces, a UK government spokesman said “there are no British forces on the ground in Syria”. However, the spokesman confirmed to The Telegraph that British jets had on one occasion engaged forces loyal to Syria’s leader, Bashar al-Assad, after SDF troops in contact had called for support. He said the situation was a one-off and if the SDF saw coalition jets as “top cover” for anything other than their fight against Isil they would likely have all support withdrawn.Such incidents are indicative of the complicated and evolving situation. An RAF Intelligence Officer admitted Isil were a resilient enemy. The group shot down a US helicopter in March, he said, and the insurgents have been known to strap bombs onto commercially-bought hand-held drones, before flying them at targets. An RAF Typhoon pilot, with over 4000 flying hours, said a simple yet robust system has been put in place to ensure British and Russian jets never get close to each other. For security purposes this mechanism will not be divulged to the public. Of the residual Isil threat, the group can “no longer weather the storm,” says an RAF Intelligence Officer. Their use of torture and human shields shows why they need to be eradicated.“Our mission is to defeat Daesh before they can export terrorism or inspire terrorism back in the UK,” says Gp Capt Dickens. Terrorism is not defined by national borders, its inspired by a narrative, he added.“If we can defeat them as a fighting force, people will not be inspired by their message.”“What we are seeing is that they are increasingly leaving the battlefield. Their experience from Iraq and Syria is that if they stay, we will target them and we will kill them from the air.” The Daily Telegraph understands the Defence Secretary is particularly concerned that Isil – also known as Daesh – might gain a foothold in Afghanistan on the back of a resurgent Taliban. The ungoverned spaces across north Africa are other areas of concern.“Daesh is facing territorial defeat in Syria and Iraq but the battle against their poisonous ideology and barbarism is not over,” Mr Williamson said.“We must be prepared as the terrorists change their approach, disperse into other countries and prepare for a potential insurgency.”Commenting on the enduring threat, Mr Williamson said: “Daesh remains the most significant terrorist threat to the UK due to its ability to inspire, direct and launch attacks. That is why we continue working through the Global Coalition to hunt down Daesh terrorists wherever they lurk.” Alongside the “overwhelming firepower” from the air, coalition ground troops support the Syrian Democratic Forces (SDF) in their effort to clear the last pockets of resistance. Groundcrew at RAF Akrotiri in Cyprus move two RAF Tornados in readiness for operations over Syria, July 5 2018.Credit:David Rose The air campaign consists of forces from 73 nations. Air Cdre Dennis says that the “fake caliphate” has been expelled from Iraq and the small pockets of resistance in Syria hold only two per cent of the territory they did in 2015.Britain is the second largest contributor to the air war. Of the 27,000 air strikes since the campaign started in 2014, around 1,700 have been from British Typhoon and Tornado fighters and Reaper drones. Voyager refuelling aircraft and Sentinel intelligence assets provide additional niche capabilities. We will target them and we will kill them from the airGroup Captain Dickens A single-seat Typhoon fighter takes off from RAF Akrotiri in Cyprus for missions in support of the Syrian Democratic Forces. July 5 2018. Credit:David Rose The Defence Secretary’s comments come as British military commanders in the region have been talking about the progress in destroying the insurgent force. Air Commodore Roddy Dennis, who leads Britain’s contribution to the air war against Isil, said the group was no longer a credible force, but needed to be stopped completely.“They’re running scared and know we’re hunting them,” he said at RAF Akrotiri in Cyprus, from where British aircraft are launched. “They are part of a target set that presents a threat to the UK and we have a government mandate to remove that threat.”“We will attrit them with ruthless precision, and for them there is only one trend: down.” Video footage just declassified by the MoD shows a strike by British Tornados on an Isil weapons facility on June 27. Two Paveway IV guided bombs were used to destroy the site. There were no civilian casualties. Britain must be prepared to fight a future insurgency unless Isil is wiped out in Syria, the Defence Secretary has warned.The Islamic State of Iraq and the Levant (Isil) insurgent group is not fully defeated, Gavin Williamson says, and if allowed to escape their “poisonous ideology” will cause further devastation if the momentum to destroy them falters.Although virtually absent from Iraq and significantly degraded in Syria, Isil fighters remain hidden in unpopulated desert areas including caves.From around 50,000 fighters in 2014, the insurgents are now thought to number only about 2,000. But they are still launching brutal attacks on civilians including beheadings, burning people alive and dragging victims behind motorbikes. The presence of Russian forces in the conflict zone has added further complexity. Group Captain Chas Dickens, the commander of 903 Expeditionary Air Wing, said a hotline has been established between the coalition air headquarters in Al Udeid, Qatar, and the Russians to “de-escalate tension”.“We recognise it requires communication to ensure no miscalculation or unusual air activity,” Gp Capt Dickens says. The hotline is used on average seven hours a week. Seen just outside the fuselage windows of an RAF Voyager tanker aircraft, RAF Typhoon fighters taking part in Op Shader refuel in theatre during a mission in southern Syria. Clearly visible on the jet is a Paveway IV laser guided bomb (the seeker head of another is seen on the far side) and an Advanced Medium Range Air to Air Missile (AMRAAM) on the aircraft’s belly. July 6 2018.Credit:David Rose Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.