Britain has quietly halted its training of Syrian rebels, reflecting growing acknowledgment among key opposition backers that President Bashar al-Assad has victory in his sights.

Troops were sent last year to join US-led programmes in Turkey and Jordan, which aimed to train 5,000 vetted moderate opposition fighters a year for three years in the use of small arms, infantry tactics and satellite communication.

The Ministry of Defence confirmed to the Telegraph that in late June the last 20 soldiers returned home from the programme, which is ongoing.

The training was part of the Pentagon’s $500m (£390m) train-and-equip programme and was established in 2015 with the aim of pushing back Islamic State of Iraq and the Levant (Isil) in the east of the country and hold on to the territory to prevent its return.

Since an offensive launched earlier this summer by Syrian government troops and their allies around the US garrison at al-Tanf, south of Isil’s last major stronghold in Deir Ezzor, the rebels have wound down operations there.

The rest went on to fight the jihadists in Raqqa.