British soldiers were “a matter of metres” from last week’s deadly bomb blast at Kabul airport – and are taking part in decompression therapy to help deal with any trauma they suffered during the dangerous two-week evacuation.

Commanding officers, speaking for the first time after returning from the Afghan capital, said it was sheer good fortune that prevented British troops from being killed in the attack alongside 170 Afghans and 13 Americans.

Lt Col David Middleton, a paratroop commander, said “the proximity between ourselves and the Americans was a matter of metres” and that “the position by which the explosion went off just happened to be in the American area”.

A leaked account of the run-up to the attack from the Pentagon appeared to blame the British for wanting to keep open the Abbey Gate, where one of two bombs went off, so the UK could complete the last phase of its evacuation.

Middleton sought to set aside suggestions of Anglo-American disagreements, saying it was “in both our interests” to keep the gate open. “We are heartfelt sorry for the Americans we were so close with and controlled that piece of ground with,” he added.

Afghanistan’s Islamic State affiliate, ISKP, claimed responsibility for the attack, which took place in the area outside the airport where people hoping to come to Britain were being processed. A second bomb exploded near the Baron hotel, which was being used by British diplomats until the day before.

Following a warning of a likely attack, western soldiers were repositioned outside the airport, the British officer said. He added: “If you’d looked at where our forces were laid out, 24 hours earlier, they’d have been far more exposed.”

A thousand British paratroopers joined more than 5,000 US troops and others to help secure Kabul airport for a fortnight to allow the emergency airlift of more than 114,000 westerners and Afghans at risk from the Taliban following the unexpectedly rapid fall of the Afghan capital in the middle of August.

The commander officer on the ground, Brig James Martin, said the soldiers, some as young as 18, had to contend with a series of “traumatic scenes” during the chaotic evacuation, where thousands of desperate Afghans converged on the airport, not all of whom were eligible to get on a flight to the west.

Martin said troops witnessed “dead women, dead children, people being crushed to death” outside the Abbey Gates and Baron hotel in an environment over which the soldiers felt they had very little control.

“The overriding situation was very difficult to influence,” he said.

Middleton said it was also “in practice, quite difficult” for British soldiers to have to turn people away, particularly in the case of Afghans who thought they had a right to come to the UK but were not going to be accepted. “My soldiers ended up sort of enacting some of those decisions, having to turn people away essentially,” he said.

Following what they had witnessed, Middleton said the troops were engaged in decompression after returning to the UK, involving a series of “relatively light-hearted lectures and guest speakers” advising the young troops “how important it is to sort of share your feelings and open up”.

Troops were being put in smaller groups, with their team-mates, the officer said, to use that as a place to raise any issues “in the first instance”, because “the last thing we’d like to do is someone to get away having a load of emotion suppressed”.

Thousands of Afghans who were potentially eligible to come to Britain were not able to be airlifted out in time, while thousands more were unable to prove their eligibility, many of whom nevertheless gathered outside the Abbey Gate and Baron hotel in the hope of being called for evacuation. Twenty people were killed in crushes during the airlift.