All three are important voices in some of the biggest issues facing the planet. Yet not one member of this triumvirate is an elected politician.

Of course, Messrs Gore and Blair rose to prominence through politics. But the former US vice-president has achieved more since he left office in 2001 on climate change than he did during his eight years in the White House.

Tony Blair now looks likely to do the same. As Gordon Brown quietly marked the end of his disastrous first year in Downing Street, his predecessor was the centre of global media attention as he launched a report on practical solutions to global warming, a topic that Mr Brown has repeatedly failed to put at the top of the world agenda.

Among his many other interests, Mr Blair is also now a key figure in the attempts to bring peace to the Middle East through his work as
envoy for the Quartet – Russia, the US, United Nations and European Union.

When historians pore over the lives of both men, they may come to the conclusion that Blair and Gore's election to high office was important primarily because it provided a stepping stone to positions where they could have a much bigger influence.

Bill Gates needs no such stepping stone, having led the computer revolution through his Microsoft empire, amassing a fortune worth billions along the way. He too, however, has just retired from his day job to focus on the work of the charitable foundation that he set up with his wife eight years ago. His vast wealth and determination are expected to see major inroads made into tackling problems such as malaria which have previously been ignored or considered insoluble.

People like Gore, Gates and Blair are part of a new breed. They areoutside the world of politics but not campaigners in the traditional sense. Neither are they fundraisers or lobbyists. These are statesmen without electorates to answer to, and that is a powerful combination.

Just 20 years ago, there was no doubting that the most powerful people were elected politicians. Ronald Reagan and Mikhail Gorbachev held the world's future in their hands. When they met, the world stopped and waited and hoped that deals would be done that would lift the shadow of nuclear war.

The end of the Cold War saw global politics fragment. Where once their were two voices that mattered, there are now dozens. And in a world where countless politicians feel they have to defend narrow national interests in the face of global problems, there is tremendous scope for internationally recognisable figures to make their voice heard.

Relieved of the burden of diplomatic niceties and protocols, or the need to seek re-election, people like Bill Clinton are able to deploy forceful arguments and clear thinking which presidents and Prime Ministers cannot or dare not use.

And while it is relatively easy for world leaders to ignore traditional campaigners, they cannot casually dismiss the views of men and women who have held high office or been hugely successful in business.

This new political class is not a replacement for their democratically-mandated colleagues. Tackling global warming will eventually require a deal endorsed by governments. The establishment of a Palestinian state will only come about when Israel and the representatives of the Palestinian people agree.

Only governments can build roads, inflict sanctions, or commit armed forces and, most importantly, legitimately claim to act in the name of the people they represent.

But the new global voices are becoming increasingly important in ensuring that governments do not take the mutually convenient decision to ignore issues they would rather not have to confront. In the absence of meaningful action from South African president Thabo Mbeki over the chaos in neighbouring Zimbabwe, it was his predecessor Nelson Mandela who supplied the condemnation of Robert Mugabe that the world needed
to hear.

It was more measured in tone than many would have liked, but it was still enough to spur the G8 leaders to promise to pursue sanctions against figures in the Mugabe regime despite Mbeki's opposition.

Many people around the world believe Barack Obama could have a positive impact on some of the key issues facing the world if he is elected president of the United States.

But, if he wins, he will have to work within the boundaries allowed by Congress at home and on the international stage will find it hard to act unilaterally when faced with a resurgent Russia and increasingly powerful China.

Senator Obama's great strength is stirring oratory, but its full potential may only be realised when he no longer has to worry about the consequences of what he says.

Winning the election in November will give him the keys to the Oval Office, but it could be that his greatest influence is only felt after he has left the White House and he joins the new breed of world statesmen.