The glass wall slides open silently and through it potters a short, slight man, smiling amiably. He sits down at the head of the long board table, leans back and lights a large Cohiba cigar. His smile widens. Right now, Lord Browne, chairman of BP, has a lot to smile about.

He may be physically small but in corporate terms he is a global colossus — and so is his company. Since he took the helm, he has led BP out from the shadow of Shell, its main European rival, to a position where it threatens to leave its competitor behind.

His reputation is more than secure, as is his company. But with just three years left before he steps down in February 2008, what must Browne do to prepare BP for life without him? Almost 10 years after he took control of BP in July 1995, Browne is Britain’s most respected businessman and his company is Britain’s biggest, with a market value of £111 billion. BP’s shares closed on Friday at 512p.

Last year the oil industry enjoyed record prices of more than $50 a barrel, a figure that some analysts expect to see again in coming months. As a result, BP’s cashflow is “staggering”, said Browne. Next month BP is expected to announce an annual pre-tax profit of $25.4 billion (£13.5 billion), a record for any British company and a 47% increase on the previous year.

Amoco and Arco, the American oil firms Browne bought in the 1990s, have finally been fully integrated. Many were sceptical when he first announced these deals. Today he has proved his doubters wrong.

Equally, despite the gloomy warnings from the City that accompanied BP’s venture into Russia in 2003, its Russian subsidiary, TNK-BP, has survived the Kremlin’s pursuit of Yukos and is pumping money back to the parent company.

Browne is also looking to expand BP’s Chinese operations, while other huge projects in Alaska and Central Asia are on the horizon.

Best of all, Shell faces questions as to whether it can survive at its current size. It was forced to cut about one-third of its proven oil reserves last year and is expected to announce further cuts when it releases its annual results next month.

Like BP in the early 1990s, Shell must find huge new reserves if it is to survive.

These difficulties have led many to speculate whether Shell is ripe for a takeover, but BP and Total, the French oil giant, are unlikely to move on their rival unless invited to do so by the board of Shell itself.

Taking a slow draw on his cigar, Browne looks content. “If we did nothing other than just carry on doing what we are doing in our existing areas, they would have huge growth for the next 10 years,” he said. “The areas we are in are very rich in terms of resources, with plenty more to do.”

Realistically, he is unable to plan much beyond those 10 years, he said. Looking back over the past 10, it is clear that he is in an industry where things change fast.

Is this as good as it gets? Browne thinks not.

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