For Wall Street bankers he lacks knowledge of financial markets. For high-technology entrepreneurs he is too old-economy. For economists he has no academic credentials.

For those who have worked with Mr Paul O'Neill, the next US Treasury Secretary, he is little short of a Renaissance man. He is lauded for his role in manufacturing and high technology, his intellectual fascination with public policy and his hands-on expertise in the global economy. Mr Richard Parsons, president of Time Warner, is typical of those who worked with Mr O'Neill in the Ford administration. "The headline is that he is one of the finest public servants I ever worked with - in terms of ideas, hard work and thoughtfulness and as a person of integrity," he says. "What has always impressed me about Paul is, even when he returned to the private sector, he has remained an active and, I think, successful thinker about public policy."

The conundrum surrounding the 65-year-old chairman of Alcoa, the aluminium titan, is how someone so experienced and so well connected could possess such a low profile - until now. Mr O'Neill admitted that he had not considered returning to public service until December and he was on nobody's list to join the cabinet until shortly before Christmas.

The tale of Mr O'Neill's return to Washington - after a 23-year absence - appears to revolve around Mr Alan Greenspan, chairman of the Federal Reserve, and Mr Dick Cheney, the Vice President-elect. The three worked closely together in the Ford White House of the mid-1970s. At the time, Mr Greenspan was chairman of the council of economic advisers, Mr Cheney was White House chief of staff and Mr O'Neill was deputy director of the budget office.

Ms Carla Hills recalls Mr O'Neill's ground-breaking work at the budget office when she was housing secretary in the Ford cabinet. Together they developed block grants that allowed the federal government to fund community projects without tying the hands of local officials. The two now sit on the board of Lucent Technologies, the troubled telecommunications equipment maker, undermining the notion that Mr O'Neill represents the old economy.

Mr O'Neill emerged from the Ford administration with an enduring relationship with his former colleagues. It was Mr Cheney who reportedly backed Mr O'Neill's candidacy as Treasury Secretary. They sit on the board of the American Enterprise Institute, the Washington think tank whose scholars include Mr Lawrence Lindsey, the President-Elect's chief economic adviser. Mr O'Neill has also stressed his long, frank relationship with Mr Greenspan, dating back to 1969. "I've made it my business at his request to come by on a fairly regular basis and tell him what I thought he was doing wrong and what I thought he was doing right."

Mr O'Neill has portrayed his role at the Treasury as a balancing act between the Fed's monetary policy, and the fiscal policy emerging from the White House - most notably Mr Lindsey's ambitious tax cuts.

It was Mr Greenspan who introduced his friend to the board of Alcoa. Mr Greenspan, also an Alcoa director, was later instrumental in the 1987 coup putting Mr O'Neill in the company's chairman.

There Mr O'Neill overhauled Alcoa's operations, reversing its strategy of diversification and slashing costs in a two-year drive that produced $1.1 billion in savings.

Describing himself as "a free-ranging, self-admitted maverick", he has spoken out on vexed issues, including his support for a petrol tax to help balance the budget in 1992.

White House officials recall Mr O'Neill's strong support for their work balancing the federal budget. They, too, have been conspicuously complimentary about him.

For sure, Mr O'Neill does not share the background of his predecessors in the Clinton administration. He is no academic like Mr Summers, and has no Wall Street experience like Mr Robert Rubin. Friends compare him to George Shultz, who moved from the White House budget office, to Treasury and secretary of state, and still found time to become president of Bechtel, the engineering company.

But it is his mild-mannered and meticulous style that stands out for his former colleagues. Roger Porter, professor of business and government at Harvard University and President Ford's economic adviser, says: "He is extraordinarily straightforward. He is not calculating. He is not manipulative. What you see is what you get."