This is the moment that General David Petraeus collapsed as Senator John McCain questioned him about recent setbacks in Afghanistan.

He returned 20 minutes later, and blamed dehydration, lack of food and jetlag, rather than McCain's questioning.

The look of terror on McCain's face indicates that he thought otherwise.

Special subscription offer: Get 12 issues for £12 plus a free copy of Andy Beckett's "When the Lights Went Out".