The burden of expectation on President Obama is colossal: the Middle East burns and millions around the world fear for their jobs and their security. Yet against the odds he is in the White House and has lit a beacon for anyone who refuses to be discouraged by people who say 'you can't' or 'it's impossible.'

Yet we must be careful. In 1997 many of us thought with Tony Blair that Britain, at last, would become a fairer, greener place. We were wrong. Blair was a massive disappointment. But, as Barack Obama himself said, let us now 'dare to hope'. Already there are signs that this inauguration represents something completely different.

Some of Mr Obama's key appointments are cause for optimism. Steven Chu, the incoming US energy secretary, has a long record of opposing coal-fired power stations while Carol Browner, who now has responsibility for climate change, is regarded in the US as a progressive radical.

In politics, 'hope' is a powerful driving force. This is a new start for US and global politics, and Barack Obama is to be congratulated on a breathtaking journey which is far from over.