LORD King, credited with transforming a lumbering British Airways into one of the world's most profitable and efficient airlines, was renowned as Margaret Thatcher's favourite businessman.

However, his bitter rivalry with the Virgin boss Sir Richard Branson, in a long-running "dirty tricks" row, cast a pall over the close of a career that would otherwise have ended in triumph. Those who knew this brilliant entrepreneur said this dispute, and BA's subsequent capitulation, left this normally ebullient industrialist both drained and demoralised.

However, before that sad ending to an illustrious career, Lord King had worked wonders with British Airways to prepare it for privatisation.

The man whose life began in a humble cottage in Brentford, west London, was to become one of the greatest captains of industry of the twentieth century.

When then-prime minister Mrs Thatcher offered him the chairmanship of BA it was losing pounds -150m a year.

He was head-hunted by her to transform this inefficient, lossmaking nationalised flag-carrier into a condition which made it saleable into private hands.

He succeeded brilliantly. King joined BA in 1981 and the major changes he brought about included removing 22,000 staff members and hiring, in 1983, Colin Marshall, a prominent British businessman, as chief executive officer. Marshall was also to play a leading role in the reform of the company up to its successful privatisation in 1987.

King also removed older aircraft from the f leet, purchased more modern and efficient airliners and axed unprofitable routes. Within two years, he had replaced more than half of the BA board with his own appointees.

When BA was privatised, the initial share offering was 11 times oversubscribed. However, all this was to be overshadowed in 1993 by the most bitter and protracted libel action in aviation history, in which BA was forced to climb down after an alleged "dirty tricks" campaign against Virgin Atlantic.

BA had to apologise "unreservedly" and agreed to pay damages of pounds -500,000 to Branson and pounds -110,000 to his airline, as well as incurring legal costs of up to pounds -3m.

The traditional rivalry between the two airlines had intensified from 1991 when Virgin moved the centre of its operations from Heathrow to Gatwick, in direct competition with BA.

By October, Branson had reportedly accumulated evidence of BA employees poaching Virgin customers and tampering with confidential company files. Branson embarked on his libel case over allegations BA had made about him, and Lord King countersued over Branson's original allegations.

King finally retired from the job in June 1993.

John Leonard King was born in 1917 in humble surroundings.

His fatherwas a soldier-turnedpostmaster and his mother made ends meet by taking in washing. Years later, he was to revel in the wealth and the social standing that his success and immensely hard work had brought him.

Ultimately, he became master of the Belvoir Hunt, friend to royalty and presidents, and his home was a 2000-acre estate in Leicestershire, a far cry from his modest beginnings.

King began his career working for a number of small engineering companies. His first step-up came in 1941while working as a salesman for a garage near Guildford, in Surrey, when he married the boss's daughter, his first wife, Lorna Sykes.

She was to die in 1969, having borne him three sons and a daughter. The following year, he married the Hon Isabel Monckton.

His business acumen was quick to shine through from the start of his career in the forties.

He was soon running his own company, Whitehouse Industries, which prospered through defence contracts, not least through King's innate industrial skills. At the end of the Second World War, aged 28, he moved to Yorkshire, where he acquired a ball-bearing company, Pollard Bearings, and built it into the third largest British company in the field. When the then Labour government forcibly merged ball-bearing companies in 1969, King reportedly walked away with pounds -10m.

Over the next decade, he established himself as one of Britain's outstanding businessmen, running Babcock and Wilcox as well as Dennis Motor Holdings.

In 1979, King was knighted and he became Lord King of Wartnaby in 1983.

Lord King, who became president emeritus of British Airways, also held numerous directorships, especially in aviation companies, both in the US and the UK.

He also played a major role in charitable and sporting activities. He was chairman of the British Olympics Appeal Committee from 1975-78, of the Macmillan Appeal for Continuing Care (Cancer Relief) from 1977-78, Alexandra Rose Day from 1980-85 and many others. He served as a trustee of the Royal Opera House Trust and the Liver Research Unit, as well as being on the advisory council of the Prince's Youth Business Trust. Lord King was also a companion of the Royal Aeronautical Society from 198587 and was granted the Freedom of the City of London in 1984.

His recreations were listed as hunting, shooting and fishing, racing and painting.

Lord King of Wartnaby;

born June 21, 1917, died July 12, 2005.