A former British soldier left stranded in Kabul is leading an escape effort for 400 Afghans across a Taliban-controlled border.

       Ben Slater, 37, decided to escape Afghanistan over land seized by the Islamist group after the Foreign Office failed to approve visas for the air evacuation of himself and around 50 staff, mainly Afghan women, from the Nomad Concepts Group.

       Mr Slater is the chairman of the group, which operates from Kabul.

       A detailed plan for the escape, seen by The Telegraph, has been sent to the Foreign Office and Ministry of Defence in the hope that UK forces will assist their efforts on the ground and repatriate them when they reach their destination in a third country.

       The location of Mr Slater’s convoy and their final destination cannot be revealed for security reasons.

       He formerly served in the Royal Military Police, where he worked as a bodyguard to British ambassadors abroad.

       “It’s going to be a long trip, and I am hoping on the other end that the FCDO have got our visas sorted, or at least have spoken to the foreign affairs ministry in our destination country to allow access for our vulnerable staff,” he said.

       Mr Slater has already helped evacuate dozens of people from Afghanistan on the UK’s airlift programme.

       But when he asked officials to organise the evacuation of himself and the 50 staff, who are at risk of retribution from the Taliban after the West’s withdrawal from the country on August 31, no visas were provided.

       He described himself as “massively let down” by the UK Government and has launched his own operation to save 400 Afghan nationals, which includes the 50 staff, and himself.

       Ministers have advised any British nationals or Afghans eligible for resettlement in the UK to attempt to make passage to countries that neighbour Afghanistan so they can be repatriated.

       But concerns have been raised that Foreign Office officials failed to adequately prepare with Pakistan, Tajikistan and Uzbekistan to allow people to travel to the UK.

       Officials are reportedly concerned that Russia has encouraged Afghanistan’s neighbours not to accept Western citizens in transit to their home countries, or to facilitate Afghan refugees seeking resettlement in Britain and elsewhere.

       The Taliban has assured world leaders they will allow people to leave the country across land borders with other states, but Mr Slater and other travellers are concerned local fighters will not keep that promise.

       A joint statement by 90 countries released on Sunday night said: “We have received assurances from the Taliban that all foreign nationals and any Afghan citizen with travel authorisation from our countries will be allowed to proceed in a safe and orderly manner to points of departure and travel outside the country.”