hello and welcome if you're watching in the uk all around the world. tens of thousands of afghan refugees are thought to have crossed the border into pakistan in the four weeks since the fall of kabul. they'rejoining a huge population of afghan refugees already in the country — 1.5 million who are registered and an estimated i million others. our world affairs editorjohn simpson has travelled through the khyber pass — to the border between pakistan and afghanistan at torkham. every inch of ground here has been fought over for 3000 years. the insignia of a former british and indian regiment of carefully preserved on along the way and the khyber is a major trade route.