In this Guardian article, Ian Jack analyses a powerful image taken during the last few minutes of Gordon Brown's reign as Prime Minister. The photo is by Martin Argles for the Guardian. (I read the article in Saturday's Guardian but unfortunately can't find a link to a bigger pic online, or the key used in the printed version.)
"The place: Downing Street's 'war room'. The time: 19.17, according to the wall-mounted TV. Three minutes later, Gordon Brown resigns. At least one person is crying in this remarkable photograph, but plenty more have cried at the sight of it. Look at the detail, and you see why."
The photo is from a series by Martin Argles
*I believe that The Guardian style guide advises that the word "iconic" should be used sparingly, but it would be appropriate if one of these photos ends up with this label.