Prime Minister Boris Johnson has said the UK departure from Afghanistan was “the culmination of a mission unlike anything we’ve seen in our lifetimes.” The final UK troops and diplomatic staff were airlifted from Kabul on Saturday, drawing to a close Britain’s 20-year engagement in Afghanistan and a two-week operation to rescue UK nationals and Afghan allies. Ambassador to Afghanistan Sir Laurie Bristow, who had been processing those fleeing the country at the airport until the last moment, was among those who landed at RAF Brize Norton base in Oxfordshire on Sunday morning. And it brought to a close Operation Pitting, believed to be the largest evacuation mission since the Second World War. In a video uploaded to Twitter on Sunday morning, Johnson praised the more than 1,000 military personnel, diplomats, and officials who took part in the operation in Afghanistan. He said: “UK troops and officials have worked around …