BARONESS Valerie Amos became the first black woman appointed to the British Cabinet on Monday, 25 minutes after her predecessor, Clare Short, resigned as international development secretary.

The speed of the announcement suggests Tony Blair had earmarked her for elevation to his top table. It also completes a rapid rise through the ranks for a Blairite loyalist, who is virtually unknown outside Westminster.

As a minister with little taste for personal publicity, she will strike a contrast with her outspoken predecessor. And Blair will hope that she can take some of the political heat out of the sensitive issue of the reconstruction of Iraq.

On Monday, however, she was unable to contain her joy over her promotion, performing an impromptu jig outside the foreign office. As the Foreign Office minister with responsibility for Africa, she had impressed the British prime minister and Jack Straw, the foreign secretary, with the quiet efficiency of her diplomatic skills.

The fact that the position was handed to a non-elected politician will raise suspicions that it is being downgraded. Despite her distaste for publicity, Amos will inevitably become a role model for black women.

Trevor Phillips, chairman of the Commission for Racial Equality, said: “I hope her appointment will be an inspiration to young black and Asian voters, many of whom currently feel disengaged from British politics.”

Julie Mellor, chairperson of the Equal Opportunities Commission, hailed the day of Amos’s appoinment an “historic day.”

She said: “I hope we will see many more black and ethnic-minority women following Valerie Amos into every level of politics. I am confident she will bring her understanding of gender issues to her new role at this crucial time for the reconstruction of Iraq.”

Amos has never attempted to steer clear of ethnic-minority issues, unlike Paul Boateng, the first black cabinet minister.

However, the British Government insisted Amos had been selected principally for her knowledge and expertise, rather than her willingness to toe the line or her race and gender. “It is a signal that the prime minister will promote and reward talent within his government regardless of background,” Blair’s spokesman said.

The prime minister is said to be particularly impressed by the work Amos has done in Africa since she was appointed a Foreign Office minister in 2001. She canvassed African leaders in the run-up to the war in Iraq, visiting Cameroon, Angola and Guinea in a bid to sell the Anglo-American stance.

This lobbying is seen by Number 10 as good preparation for the new international development secretary’s work on the reconstruction of Iraq — one of the most important and difficult issues in her in-tray.

But critics pointed out that a knowledge of the brief may be of little use unless Amos is willing to stand up to her new cabinet colleagues. The Tories expressed alarm at the stature of the new secretary of state. Her status as a political appointee — Amos was made a life peer in 1997 — rather than a democratically elected MP was in “danger of downgrading” the post, the Conservatives warned.

In a rare interview, Amos once said: “It is always useful to know one’s history. I also think that it is important to be clear about the values and principles which underpin one’s life. And be clear about where you want to be and how to get there.”

Amos was born 49 years ago in Guyana. Her parents emigrated to Kent when she was 9. She has a degree in sociology from Warwick University, and a master’s degree from Birmingham University.

After working in equal opportunities, training, and management services in local government, she became the chief executive of the Equal Opportunities Commission from 1989 to 1994. She set up her own consultancy, with clients including the South African Government.

She was made a life peer in 1997, taking the title Baroness Amos of Brondesbury, and became a whip in the Lords a year later.

After the post-election reshuffle of June 2001, Blair plucked her from obscurity in the Lords. Her considerable personal charm won her admirers on all sides of the House.

At the Foreign Office, she was given a portfolio that included Africa, the Caribbean and consular issues.

Much of her time was spent on Zimbabwe, with her color making it harder for the Mugabe regime to accuse Britain of pursuing a post-colonial agenda.

One of her colleagues said: “She is competent and relaxed and very much on top of her brief.

“Unlike some I could name, she didn’t try to get a lot of publicity for herself. She has certainly earned her spurs.”

Amos inherits a formidable agenda from her predecessor Clare Short. Iraq — where the United States has perverted aid spending into a billion dollar bonanza for some of the White House’s closest corporate allies — is a test for the future of multilateralism and the United Nations. Short was a player in that debate within cabinet but Amos, with her Foreign Office roots and dependence on the prime minister’s patronage, may find it more difficult to hold an independent line.

Amos faces other serious challenges. This is the year when the Group of Eight Nations is meant to deliver its promises to Africa. But the war on poverty is being sidelined by the war on terror and all the signs are that the G8 will fail to meet even last year’s commitments, let alone deliver fresh aid. That failure will be all the more stark, by comparison, with resources spent waging war on and then rebuilding Iraq.

Finally, the new international development secretary must confront the failure of political will that is the Doha round of negotiations. If a tenth of the effort that went into the diplomatic manoeuvrings preceding Iraq had gone into breaking the deadlock over the rules on importing cheap drugs for the world poor and cutting agricultural subsidies, the talks would be steaming along. Amos’s diplomatic skills face a stiff test in a high profile role.