There was more than a hint of triumphalism last week as Sir John Browne, chief executive of BP Amoco, Britain's biggest company, took to the stage of London's Mermaid Theatre to give yet another performance as the takeover king of the international oil industry.

The script was somewhat different from the one Sir John delivered on a sweltering day last August when he startled the world's oil industry and jolted the markets with his takeover of Amoco of the US - which was then the biggest industrial merger in history.

Last year he spoke of the need to move the former British Petroleum into the oil "super league", alongside arch-rivals Royal Dutch/Shell and Exxon. He said last week's $26.8 billion (#24.8 billion) takeover of Los Angeles-based Atlantic Richfield (Arco) was more an exercise in filling the gaps in BP Amoco's global asset base.

But the boldness of the acquisition surprised many in the industry. It came only three months after the formal integration of BP and Amoco and at a time when the recovery in oil prices from recent 12-year lows is still tentative.

Sir John likes to ascribe BP Amoco's success to teamwork and good management systems. That may be so. But teamwork alone cannot explain how, in the space of less than eight months, the former BP has transformed itself from a production company in Britain and the US into a global energy group, with a large and balanced international portfolio of oil and natural gas assets.

This astounding transformation, industry insiders agree, was possible largely because of the undisputed respect and authority Sir John commands in a highly competitive business.

"It's an incredible example of the management premium in BP Amoco's share price being used as an acquisition currency," says one admiring merchant banker.

How did Sir John earn such a sterling reputation in just 3 1/2 years at the helm of BP, and then BP Amoco?

Sir John has benefited to some degree by retaining, and refining, a few simple principles laid down by Lord Simon, his predecessor, now a minister in the department of trade and industry. The first is to set clear and realistic financial and performance targets.

The biggest crime a senior manager can commit in BP Amoco is to fail to give Sir John ample warning that an agreed target will not be met. Critics say he is autocratic and rules by fear. Supporters insist his business acumen and managerial skills more than offset his autocratic bent.

As for ruling by fear, they say it is an exaggeration, although one colleague concedes that Sir John does "engender a certain amount of trepidation".

Sir John has also followed Lord Simon's practice of maintaining a continuous charm offensive with the markets. There are rarely any nasty surprises from his company.

Instead investors are expertly drip-fed a series of pleasant surprises, while bad news - such as write-downs on questionable investments - are usually tucked away amid a welter of positive developments.

Sir John has also brought his own qualities to the job. It was his decision to break ranks with many other international oil companies and publicly acknowledge that the threat of global warming was real and that action needed to be taken, even if the scientific evidence was inconclusive.

Positioning BP Amoco as the most "progressive" company in a mature, conservative industry was a deliberate act, industry analysts say, intended to set it apart in the minds of consumers and governments.

Sir John may not personally embrace the full environmentalist agenda, but the strategy has helped cement his status as the undisputed leader of the western oil industry, and given him a public pulpit from which to further enhance BP Amoco's reputation.

His sheer capacity for work - and apparent enjoyment of it - are well known. An engineer by background, he admits to being "data driven". Colleagues say he can assimilate enormous amounts of detailed information, but in a way that, so far at least, does not seem to be at the expense of strategic thinking.

One colleague believes his business skills are of an order not seen in the international oil industry since the early decades of the century. Although he has been with BP his whole career, his instincts appear more entrepreneurial than bureaucratic. The way in which he has orchestrated the two takeovers illustrates the point.

At the beginning of last year, BP's strategy of wholesale cost cutting and volume growth was in danger of running out of steam. The oil price collapse occurred just as Sir John's frustration at the slowing pace of organic growth was rising.

Although low oil prices would come to ravage BP's earnings, Sir John knew that their impact on less fit companies than BP would expose deep-seated structural and managerial shortcomings. He also knew that the proven BP cost-cutting system would deliver billions of dollars of additional savings if it could only be applied across a bigger asset base.

But boldness was needed to break the industry's structural logjam, as there had not been a big takeover among the "seven sisters" of the international integrated oil industry since the 1980s.

Although people joke that Sir John is simply working his way through the alphabet of American oil companies, Amoco was a logical starting point. It had good assets, but its management system had atrophied in recent years, with internal processes taking precedence over business operations. And there was no obvious successor to Mr Larry Fuller, its long-serving chairman and chief executive who was nearing retirement.

Sir John's gamble paid off. The Amoco takeover caused BP's share price to soar even as oil prices tumbled. And it is the market's confidence in Sir John's management, reflected in the share price, which allowed BP Amoco to make its all-share bid for Arco.

Executive succession problems at Arco were one of the factors that caused its management to seek a deal with BP Amoco. The fact that such problems played such central roles in the two takeovers has prompted Sir John - who is not due to retire for more than nine years - to begin thinking about preparing the ground for his own departure.

"A key role of a chief executive officer is to prepare the succession," he said last week, as he relaxed with a cigar at the Mermaid Theatre. "It's never too early to start." But the oil industry is betting that there will be a few more performances of the takeover king before he bequeaths his crown.