It has always been a threadbare strategy, born of wishful thinking and wilful ignorance. One of the many scenarios that it did not countenance was the orderly transition of authority while Castro was still alive. Insofar as this possibility was examined at all, it was dismissed on the grounds that he would never willingly cede the power which he had exercised for more than 40 years, at every level of detail in Cuba's affairs.

The startling truth to which the US will eventually have to adjust, and which the British government should urgently recognise, is that the transition has already taken place. Castro's ill health created the context in which power passed seamlessly to a group of his most trusted and experienced colleagues. There is no longer any need to speculate about the post-Castro order, far less try to manipulate the outcome. It is already in place.

When Fidel Castro eventually dies, there will be outpourings of heartfelt sorrow among the Cuban people. However much it dislikes them, Washington will do well to pay more attention to these sentiments than to the whoops of celebration in Miami. For the Cuban masses who mourn Castro are not going to turn on his appointed successors.

All of these people, most of whom I know and respect, have been to the forefront in Cuban domestic life for decades. Even if they do not aspire to the charisma and stature of Fidel, they enjoy far more popular recognition and support than the Americans admit. And there is not the slightest evidence that US interference in Cuban affairs post-Fidel, even among those who want to see change, would be any more welcome than it has been for the past 45 years.

The collective leadership that has emerged since last July is headed by Raul Castro, Fidel's 75-year-old brother, who has long had responsibility for the armed forces. But the Cubans are pragmatic people and they know that Raul might not be around for long either; hence the transition to collective leadership. It is made up of men who fought by Fidel's side years ago and retain legendary status, alongside younger, more technocratic members of government.

Carlos Lage, a paediatrician by profession and de facto prime minister under Fidel, has taken responsibility for the key energy sector. He is a first-class organiser and communicator. Francisco Soberon, the governor of the Central Bank, is a sophisticated operator who has been making the books balance against all odds for years. I first met Felipe Perez Roque, the fiery and articulate foreign minister, when he was Fidel's private secretary. There are women like Yadira Garcia, responsible for natural resources.

Believe me, these are high quality people who would be assets to any government - and are now firmly in control of Cuba. Each of them is ideologically committed to maintaining Cuba's independence and political system. But none of them is the unbending ideologue of Washington caricature, far less an authoritarian denier of human rights. They will display pragmatism and flexibility but will certainly not roll over and allow the fundamental reforms of the Cuban revolution to unravel.

So where does Britain stand? Sadly, yet again on the Americans' coat-tails. I well understand the imperatives that oblige Britain generally to be on the same side as Washington in international affairs. But it always struck me that Cuba was one matter on which we could have developed a constructive foreign policy without calling that wider relationship into question.

During my time in government, I tried to normalise UK relationships with Cuba in areas such as trade and energy, while excellent diplomatic relations were spearheaded by the then ambassador in Havana, David Ridgway. Without deviating from the formal positions of either government, it was possible to open up areas of discussion and cooperation on the basis of mutual respect.

But then all of that changed. The Foreign Office chose to become involved in the EU's diplomatic offensive against Cuba, led by prime minister Aznar of Spain, and in line with American policy. Though Spain has moved on with its Socialist government, and the EU policy has softened as a result, Britain repeatedly allies itself with the most right-wing governments in Europe on Cuba. Our embassy in Havana is shunned by Cuban ministers, and other avenues of cooperation have virtually disappeared.

No one in a senior government position in Britain has any first-hand knowledge either of Cuba or of the people who run it. Our influence is zero, because we have chosen to accept the Washington orthodoxy that regime change is just around the corner.

Ostensibly, the justification for this position is concern about Cuba's record on human rights. When Margaret Beckett made her first major speech as foreign secretary on human rights it was, remarkably, Cuba that was given pride of place in her remarks. Our glorious ally, Saudi Arabia, did not even merit a mention. Not only the Cubans are entitled to complain about this epic display of double standards. The British are too.

The Americans' camp followers on Cuba have never been prepared to acknowledge that a country which has lived under constant economic siege for almost half a century, and which has been subject to more foreign plots than any other, might be entitled to define "dissidents" in terms that do not match those of their persecutors. But the obvious point is that dialogue might produce results, as it has done in the past, while the current stand-off, based on mimicry of Washington, will certainly yield none.

By recognising that regime change will not happen, and cannot be forced by external intervention, Britain could restore mutually respectful relationships with Cuba. There is still time. But if our sole objective is to destabilise the Cuban government and support American manoeuvres to replace it, there will be no point in even going to the funeral. Because nobody will even speak to us, except the man from the CIA.

Brian Wilson is a former Foreign Office minister and was the only member of the government to maintain regular contact with Cuba between 1997 and 2005.