Dominic Raab is a clever man, but not perhaps a wise or especially honourable one. Chronic misjudgments over Britain’s withdrawal from Afghanistan necessitated his sacking as foreign secretary. Yet Boris Johnson, his Brexiter pal, immediately gave him another cabinet plum and made him deputy prime minister. For those he had failed, it was a contemptuous slap in the face.

Instead of clinging to office, Raab should have resigned from government. It’s not too late to do so. Official cables from Britain’s ambassador in Afghanistan, published last week, confirm that Raab, if he had been fully paying attention, could have foreseen and more effectively managed the consequences of the rapid Afghan government collapse and the fall of Kabul on 15 August.

If Raab had done his job properly in crucial preceding weeks, and not compounded his neglect by going on holiday to Crete on 6 August, the final evacuation from Kabul might have been less chaotic. Fewer Afghan nationals who loyally served Britain might have been left to the Taliban’s mercy. Thousands of emails pleading for help might have been acted on. The UK’s reputation as a trustworthy, competent ally might not have been so thoroughly trashed.

It’s impossible to turn back the clock. But it’s important to set the record straight, and it’s simply untrue to say, as Raab, senior officials and government spokespersons do, that no one saw the collapse happening so quickly. Sir Laurie Bristow, the UK ambassador, did. On 28 June, he warned the Taliban were making rapid territorial gains and “seem to be positioning … to take major population centres”. On 13 July, he reported they held Afghanistan in an “economic noose”.

On 2 August, four days before Raab headed for Crete, Bristow rang the alarm bells more loudly still. Afghan security forces were unable to hold back the insurgents, he cabled. “We are entering a new, dangerous phase.” He stressed the need to focus on relocating “those who have worked for us” since 2001.

Raab was by no means short of additional advice and expertise, domestic and foreign. In April, Gen Sir Nick Carter, chief of the UK general staff, voiced serious misgivings about the withdrawal. Gen Kenneth McKenzie, commander of US central command, says he warned both Donald Trump and Joe Biden of an “inevitable” collapse. In June, Robert Gates, a former US defence secretary, urged a rethink.

In July, the CIA’s view that President Ashraf Ghani’s government was in “serious jeopardy” leaked to US media. Ben Wallace, the defence secretary, said he concluded that same month that the “game was up”– and that evacuation plans must be accelerated. Military leave was cancelled on 23 July. Yet following Raab’s example, top Foreign and Commonwealth Office officials looked the other way and went on holiday.

In the months before Kabul fell, Raab did not visit the region, nor did he speak to his ambassadors there. He either ignored or did not read the Foreign Office’s own risk assessment, dated 22 July, that warned the Taliban advance could lead to “fall of cities, collapse of security forces, Taliban return to power, mass displacement, and significant humanitarian need”. Why?

Even Observer readers were more up to speed than Britain’s foreign secretary. On 20 June, under the headline “Catastrophe stalks Afghanistan,” I wrote in this column: “Kabul itself may not be safe for long, according to gloomy CIA and military intelligence assessments … [But] western politicians, including in the UK, shield their eyes. They don’t want to see, let alone discuss, what’s about to happen.” I was of course referring to Raab.

The mishandling of the withdrawal aside, Raab’s arguably more fundamental Afghan blunder was his apparent failure to oppose, or even query, Trump’s foolish 2020 decision to cut and run or Biden’s subsequent, reckless adoption of a September 2021 deadline. Military chiefs and senior Tories complained the Afghan people were being abandoned. Wallace believed Trump had made a “rotten deal”.

Yet possibly out of excessive deference to Washington, or because Johnson needs a post-Brexit US trade deal, or because he believed the Afghan project was unviable, Raab failed to speak out. Sir Iain Duncan Smith, a former Conservativeleader, says the US closure of its Bagram airbase, for example, was a key tactical error that gave free rein to Taliban ground forces, as Bristow had warned it would.

“The question now is what did the foreign secretary do and did anybody in the government say to the Americans, ‘This is going to be a disaster if you close Bagram’?”, Duncan Smith said in the Times last week. Another question is why Raab did not support Wallace’s unsuccessful attempt to persuade other Nato countries to maintain a presence after the Americans left.

The deteriorating, post-withdrawal situation in Afghanistan is a daily rebuke to Raab and Johnson’s government. The Taliban’s political isolation, a freeze on $9bn (£6.5bn) in national assets, foreign aid cuts, and the onset of winter foreshadow a humanitarian catastrophe and economic collapse.

A new refugee crisis threatens to engulf Europe’s borders, terror groups operate with impunity, women’s and civil rights are overturned, and China, Russia and Iran are plotting a future dictated by them. Hundreds of people for whom Britain has responsibility remain trapped and desperate.

Meanwhile, the House of Commons foreign affairs committee is pursuing its inquiry into what its chair, Tom Tugendhat, describes as Britain’s “single biggest foreign policy disaster since Suez”. Addressing an initial hearing last month, Raab –unrepentant, arrogant, tetchy – said: “I struggle with the Suez analogy.”

Perhaps Britain’s august deputy PM would be more comfortable with a different historical parallel: the failure to foresee Argentina’s invasion of the Falklands in 1982. As foreign secretary at the time, Lord Carrington took full responsibility and resigned. He was an honourable man.