Smoke rises from an Isis car bomb in Fallujah. British special forces based in Jordan frequently cross into Syria

British special forces are on the front line in Syria defending a rebel unit under daily attack by Isis, military commanders have told The Times.

The operation marks the first evidence of the troops’ direct involvement in the war-torn country rather than just training rebels in Jordan.

British special forces based in Jordan frequently cross into Syria to assist the New Syrian Army (NSA), which has been holding out in the southeastern village of al-Tanf. The rebel unit, made up of former Syrian special forces who defected from President Assad’s army, was retrained by the British and Americans.

The Times reported last week that British special forces inside Libya had destroyed two Isis suicide vehicles in Misrata, demonstrating that, despite having a training, intelligence-gathering