Before the deal, BP boasted a turnover of £43.5bn ($71bn), had 56,450 employees world wide and produced 1.25m barrels oil per day.

BP started in the Iranian desert 90 years ago

The Amoco merger propels BP into a new dimension and is possibly the high point in the history of the company which was first registered in 1909 under the name Anglo-Persian Oil.

But the company's origins go back to 1901, when a wealthy Englishman, William Knox D'Arcy, ventured into the Iranian desert to search for oil.

For seven years, Mr D'Arcy battled with difficult terrain, an uncertain political situation and rising costs.

But in 1908 the venture found oil in southwest Persia. One year later, Anglo-Persian Oil was formed.

However, by then most of the company was owned by the Burmah Oil company.

Government backing

Shortly before World War I, Anglo-Persian managed to find a new backer - and good customer.

After lengthy negotiations, the oilmen promised Winston Churchill, then First Lord of the Admiralty, secure supplies of oil.

In exchange the British government injected £2m of new capital into the company, acquired a controlling interest and became de-facto the hidden power behind the oil company.

The years between the wars were an era of expansion, with exploration in Canada, South America, Africa, Papua and Europe.

In 1935 the company was renamed Anglo-Iranian Oil Company.

Winston Churchill saw the importance of BP as the navy switched from coal to oil

British Petroleum

1951was a crucial year in the company's history. Iran decided to nationalise the company's assets, which back then were the UK's largest single investment overseas.

Three years later the conflict was resolved - in the same year that the company was renamed British Petroleum Company.

The Iranian crisis had convinced BP that it had to broaden its activities. In the following years the company started explorations in other Middle East countries, like Kuwait, Libya and Iraq.

But its most important moves were into the North Sea and Alaska in the 1960s.

Finding oil in British waters and discovering the biggest oilfield in the United States at Prudhoe Bay in Alaska transformed the company.

These finds put BP into a position to survive the impact of the two oil price shocks of 1973 and 1979, even though the new oil fields did not come on stream before the mid-seventies.

But the success led to over-confidence. Rash investments in the 1980s bloated the company's overheads. By then, the government was no longer involved in the company, having sold its last shares in the company in 1987.

In 1992 the group posted a loss and had to embark on a drastic cost-cutting exercise.

Going "downstream"

A new management, under Lord Simon of Highbury, Peter Sutherland and later Sir John Browne, set tough targets for debt reduction, profitability and cost-cutting.

Four years later profits trebled, and BP had managed a turn-around - moving from the bottom of the industry into the top quarter.