ITV News Politics Editor Robert Peston on the "sombre" mood among MP's during the debate
There were a number of jaw-dropping and historically significant moments in today's emergency debate on the Taliban's takeover of Afghanistan and the UK's withdrawal from the failing state. For me, the most important was when Boris Johnson's predecessor as prime minister, Theresa May, asked the PM whether "our intelligence was really so poor", as not to have warned him of the high risk of rapid Taliban victory and capitulation of the country's government. Ms May does not fly kites. And as a former premier and long serving home secretary, her intelligence connections are impeccable. She would not have put this question forward if she did not have some reason to believe that the PM and Downing Street may have ignored red flags from the intelligence services.
Her question felt like an inversion of the so-called "dodgy dossier" charges that did so much harm to the reputation of Tony Blair as prime minister.
The allegation against him was that he inflated the clear and present danger from Saddam and Iraq to bolster the case for the UK and US invasion, compared to what good intelligence was actually indicating. The analogous insinuation is whether Mr Johnson paid enough heed to whatever his intelligence and security services were telling him about the dangers from the precipitous withdrawal of US and UK troops from Afghanistan. Putting this in the relevant technical terms, what probability did the government's Joint Intelligence Committee (JIC) put on an ultra rapid Taliban victory. Did it say it was "possible" or "likely"?
According to sources, the JIC, its members and their opposite numbers in Washington are known to have feared that Biden's decision to withdraw all military personnel speedily and without conditions brought serious risks.
Whether or not they forecast the collapse of the official government in days, they did anticipate Taliban hegemony. So the questions about the quality and assessment of intelligence for Downing Street are also questions for the White House.
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Mr Johnson said he does not want a public inquiry into all of this. But the pressure for one may become irresistible. There were two other highly significant lessons from the debate. One is about the UK's relationship with its most important ally, the US. That relationship looks shockingly bad, for two reasons.
First, the PM did nothing to dispel the widespread fear that the US engaged in no serious discussion with the UK over the timing and mechanics of a withdrawal decision that would have huge ramifications for the welfare of Afghanistan's people, the UK and the security of the world. Britain was relegated to the position of a poodle, with no option - as the PM conceded - but to retreat in haste, when its master called time. Why didn't the PM or the foreign secretary try and negotiate with the Biden administration an alternative to wholesale precipitate withdrawal, perhaps a stop gap arrangement involving other nations' forces alongside a diminished US presence?
This could have been face-saving for Biden. And even if it didn't succeed, surely it would have been better for the UK government to have tried and failed? Wasn't the whole point, for Mr Johnson, of leaving the EU to give the UK more freedom to flex its independent diplomatic muscles? Instead, the UK stayed in bed. As Ms May (again) damningly put it: "We boast of 'global Britain'. But where is 'global Britain' on the streets of Kabul?" The implication, which is worrying, is that Mr Johnson and his team simply doesn't have the kind of close relationship with the White House that would permit those discussions. And by the way, the savage criticism directed at Biden by MPs today - particularly for the way he denigrated the valour of Afghanistan's soldiers - is unlikely to help Mr Johnson build those bridges. But that is not to say the Tory MP Tom Tugendhat was wrong when he called Biden's words "shameful". Finally, today was a painful rite of passage for Mr Johnson, perhaps the first time since becoming prime minister, where he struggled to find friends anywhere in the Commons. Ms May, who caused him so much difficulty today, may have been reminded of those Brexit debates that caused her so much misery. Mr Johnson, who rather more than Ms May likes to be liked, will be chastened.