Britain, like the United States, failed to predict how swiftly the Afghan government would fall, so it had not made sufficient preparation for the chaos that would follow when the Taliban seized the capital on Aug. 15.

source https://zeenews.india.com/world/uk-did-not-expect-kabul-to-fall-to-taliban-this-year-says-foreign-minister-dominic-raab-2390463.html