David Cameron, the new Tory leader, may be publicly distancing himself from his predecessor, seeking to brand himself the centrist “heir to Blair”. But such is the former Prime Minister’s enduring popularity in America that her political legacy has now been exported across the Atlantic.

In Britain the Thatcher Foundation closed down two days after last year’s general election: funding had all-but dried up. The Margaret Thatcher Charitable Trust shut up shop in 2003, having not reported any trading activity since the end of 1999 when its gross income was just £299.

In Washington, by contrast, the right-wing Heritage Foundation recently set up the Margaret Thatcher Centre for Freedom endowed with a $3 million (£1.7 million) gift that the US-based Thatcher Foundation had raised from American admirers. Heritage promises to raise an additional $6 million for the centre and has received $4.3 million of this from more than 30 wealthy benefactors.

That means the only significant Thatcher legacy left in Britain — apart from the former Prime Minister herself — is the Margaret Thatcher Archive Trust, which manages her papers stored at Churchill College, Cambridge. It is now cross-subsidised by the Thatcher Foundation in America.

Tory relations with the Republican Party have become distinctly frayed since those heady days when Margaret Thatcher and President Reagan led the Free World’s fight against Communism.

They reached their nadir when Michael Howard, David Cameron’s immediate predecessor, attacked Tony Blair — and implicitly the US Administration — over the Iraq war. President Bush and Karl Rove, the President’s chief adviser, were furious and Mr Howard was told that he would not be welcome at the White House.

This week’s visit by William Hague, the Shadow Foreign Secretary, George Osborne, the Shadow Chancellor, and Liam Fox, the Shadow Defence Secretary, is intended to restore their party’s links with the Republicans. Significantly, the Conservative delegation is not seeking a meeting with the President. The three men will instead speak to Mr Rove today, and Mr Hague hopes to see Condeleezza Rice, the Secretary of State.

Yesterday John Hulson, a senior fellow at the new Thatcher Centre in Washington, said the visiting Tories were taking “the first step on a very long climb” back into the Republicans’ good books. He said that since Mr Reagan’s death, Lady Thatcher’s importance as a “totemic figure of freedom” for American conservatives had only increased. “Like Gorbachev, who has statues to him in Germany but none in Russia, Lady Thatcher is far more popular across the world than she is in her own country.”

Dr Fox, who has done more than most British Conservatives to maintain lines of communication with the US Administration, will invoke the names of both Thatcher and Reagan today in a speech to the Thatcher Centre.

Nile Gardiner, another senior fellow at the Thatcher Centre, said that Mr Cameron’s centrist domestic pronouncements were less important to the US than the more robust foreign policy positions the Conservatives are now adopting on issues such as the treatment of terror suspects.

“The Tories have spent several years in the wilderness over here. But the White House is interested to see what they will do on Iraq, Afghanistan, and most importantly — Iran. There is a growing awareness that Blair is on his way out and there is not much faith in Gordon Brown. This Administration may yet need the support of British Conservatives again.”

Baroness Thatcher, like the old London Bridge, is an unwanted piece of British heritage which has found sanctuary in America. The one made of stone languishes in the Arizona desert. The other — mythically made of iron — could still be of use to her party.

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