Barack Obama burst onto the national stage four years ago with a speech describing himself as a skinny guy with a funny name and an improbable life story.

Last night, in a return to the Democratic convention stage, the 47-year-old US senator takes his place in the history books as the first black presidential nominee of a major political party.

For many, he embodies the American Dream, in which anybody can grow up to be president, including the son of a Kansas mother and an absent Kenyan father with an exotic name who spent his early years living abroad.