Thanks to Sir Andrew, it is now socially acceptable to discuss this subject rationally. With much prodding from MigrationWatch, it has been officially confirmed that 83 per cent of projected population growth in Britain will come from mass immigration, adding six million people to these islands over 27 years. This will have enormous consequences for public expenditure, for the NHS, for crime — in short, for almost every aspect of state policy. For example, immigration will account for nearly a third of new households, requiring 1.5 million further homes over the next two decades. If this isn’t fair game for discussion, what is?

Sir Andrew has accomplished all this on a shoestring budget — and with amazing rapidity. Ralph Harris and Arthur Seldon, of the Institute of Economic Affairs, one of the most successful think-tanks of all time, laboured in the vineyards for nearly 30 years before their faith in the free market became accepted. Yet MigrationWatch has managed to “mainstream” the case for a much tougher immigration policy in less than five.

How has Sir Andrew done it? The key to his success lies in his CV and personality. Unlike Norman Tebbit, his critique cannot be dismissed by the liberal Left as deriving from lower-middle-class sourness. For he can boast an impeccable mandarin background — Haileybury, Cambridge, the Royal Green Jackets, the Middle East Centre for Arab Studies (nursery of Foreign Office Arabists) and 35 years in the Diplomatic Service, including stints as Ambassador in Syria and Saudi Arabia. In retirement, most denizens of the “Camel Corps” would have opted for a cushier and more lucrative life.

Instead, Sir Andrew chose one of the most dangerous and exposed spots on the political battlements. During his last posting in Whitehall, he was much vexed by the case of Muhammad al-Masari, of the Committee for the Defence of Legitimate Rights, an extreme Islamist group dedicated to the overthrow of the Saudi monarchy. Al-Masari had been granted asylum in this country and, in 1995, the Tory Government sought to deport him on the ground that he constituted a threat to British interests. The move was stymied by a judiciary that stuck rigidly to the letter of the 1951 UN Convention on asylum — and Sir Andrew got thinking about the system.

His other great asset is his apparent coolness. This astringent, non-partisan Arabist does not turn up the rhetorical heat: in fact, he does the very reverse. He soberly produces a stream of academic position papers on every aspect of the debate. These include demolition of the economic case for further migration; how bringing in lots more people will not help to solve the growing pensions crisis; and the opportunities afforded to terrorists by a well-nigh open-door policy.

Aided by such leading authorities as David Coleman, Professor of Demography at Oxford University, and Professor Roger Williams, director of the Institute of Hepatology at University College London, Sir Andrew relentelessly trawls official publications and statistics. These include such sources as the Labour Force Survey, the Health Protection Agency and Law Reports. If anything, he plays down the explosion in numbers. And he has had the bleak satisfaction of seeing his warnings swiftly vindicated. This was exemplified by his paper in January on the weaknesses in the system of deporting foreign prisoners once their sentences expire.

His experiences say much, also, about the way in which new Labour approaches public policy. When MigrationWatch started exposing the vast black hole that is the Home Office, the department’s response was to play the man rather than the ball. Instead of fixing the system, the Government sought to fix Sir Andrew, implying that he was racist. After a series of scandals, the new Home Secretary, John Reid, has now “discovered” massive administrative incompetence in his department. But the issue goes far beyond mere bureaucratic failure.

Rather, what we are dealing with is a massive failure of political will. The public wants action, but the odds are stacked against it, in the form of ideological multiculturalists, the human rights lobby, bureaucratic inertia and big business seeking cheap labour. The first two are well represented within new Labour, it presides over the third and has come to an accommodation with the fourth. Meanwhile, the segment of society most affected by immigration and which returns Labour to office time after time — the white working classes — has been marginalised.

That is why Sir Andrew Green is so important. The story of too much of British political life in the postwar era is how the elites have circumvented the popular will. The public resembles a muscular, but slow-witted giant, whose will is repeatedly thwarted by the cunning wiles of a bantamweight kickboxer. Sir Andrew’s current career shows that if the people are to have their way, the struggle must first be prosecuted via “insiderist” strategies within the elites. Not for him the trahison des clercs.

Dean Godson is research director of the Policy Exchange think-tank

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