Dear Barack,

You did it. You have achieved a victory that many said would never happen. This moment fills me and people around the world with a renewed sense of hope and possibility - in what you can do as President, what you have already done as a man and what others may achieve in your wake. And at a time of pessimism and uncertainty, something suddenly feels bright.

People will always claim that they always saw something special in those who transform the political and cultural landscape. I have often suspected that this is the sentimental afterglow of fame and success, but now I wonder. When I first met you at a gathering of Harvard law alumni, heard you speak, listened to your ideas, witnessed your courage and vision, discussed with you a shared hope for a new kind of politics, I came back from America and told people that I believed the first black president was already waiting to step forward. They thought I was mad.

When I met you on the campaign trail earlier this year, on a snowy Wisconsin college campus, it was clear you realised that your moment - and America's moment - had come. As you roamed the stage, addressing a spellbound crowd, people saw a president in waiting. You took time to meet local people and to thank an excited group of young volunteers, much to your minders' frustration. Popularity can distort character but it was clear that you had lost none of the humanity of the junior senator who once enlisted me on a quest for Harry Potter's autograph for a small constituent in his own home.

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BACKGROUND

• Bush - 'We should all be proud of Obama'

• The challenge that greets Obama

• Full video and text: Obama's victory speech

• Voters honour Martin Luther King's dream

Multimedia

• Team Obama - who are they?

• Bonjour 'Barack'

This ability to be at once approachable and impressive reverberated around the world during your campaign. Millions of young people discovered politics for the first time. You were familiar enough for them to feel connected, yet extraordinary enough for them to feel inspired. You gave a voice to many who had rarely been heard, and reawakened an optimism in the power of politics to change lives for the better.

You did not talk publicly about any aspiration to become the first black president, but you understand the power of your story. Through your own achievements, you have broken through an historic barrier and made a reality of the American Dream. Millions of people will see you as an example that no life need be dictated by background or precedent, but only by ability and determination. My own two sons will now grow up believing anything is possible - and for that alone, I am today filled with immense pride.

These are things that you will never forget even as you make history. But the biggest battles are still to be won. Perfecting the Union at home will understandably be your first priority. But from West to East the watching world looks at America with fresh eyes. It can believe again in an America that is a force for good in the world: the ally that helped to liberate Europe in its time of need; the nation that was the driving force behind the creation of the United Nations; the country that extended a hand of friendship to war-torn economies around the world in the aftermath of the Second World War and again after the final collapse of the Berlin Wall.

The deep reserves of American virtue need to be tapped once again and now more than ever. An economic shock of historic proportions will cause us to reconsider the rules and the values that we live by. A war-torn Middle East scars this generation and the next. Millions remain imprisoned by poverty in Africa. Our planet suffocates from carbon emissions and consumption that it cannot sustain.

These problems will not be solved quickly or easily. Their solutions lie beyond the power of one nation, let alone one man.

The expectations that you now face are colossal. More than this, the political process has a habit of distancing political leaders from the lives that they once led and the causes that brought them into public life. The machinations of getting things done can easily distract from our core mission, which is what will really count. And as you know more than anyone, too many people are invested in the old politics to let it go easily. Some will lose faith and cry betrayal. And if scepticism is an enemy, then idealism can be a critical, sometimes fickle friend.

Yet, at their best, political leaders can transcend these difficulties. They never forget that small changes can make big differences to people's lives. And they embrace the great causes of their age, aiming for the moon no matter how daunting the task looks.

In the end politics is not the art of the possible: far from it. It is the art of making things possible. Invested in you is more power than in anyone else alive. I know you will spend it wisely.

Yours ever,

David

David Lammy is MP for Tottenham and Minister of State for Higher Education and Intellectual Property

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