Only a handful of companies, including Glaxo Wellcome, BTR and ICI, have come near them since these awards were launched by the market research company MORI and PA Consulting's Sundridge Park management centre in 1993. Nor is it only this league that they dominate. They also appear to be close to the top of Europe's list of best-performing companies and succeed by all manner of financial yardsticks in addition to their strengths in brand development, people management and the rest.
M&S, of course, has been successful for generations, whereas BA joined this exclusive club comparatively recently when it was transferred to the private sector in the early days of the Conservatives' privatisation programme. But how do the two companies keep up their record, year in, year out?
Sir Richard Greenbury, chairman of M&S, and Robert Ayling, managing director of BA, both said when receiving their prizes earlier this week that at the heart of their success lay a total commitment to the customer. BA's weekly management meetings apparently start with a review of the previous week's customer complaints and of the action being taken to deal with them. At M&S the notion that the customer pays everybody's salaries is drilled into every member of staff.
Both companies acknowledge that their very success attracts the best recruits. But they are also constantly on guard against complacency. Huge investments are made in training, with the aim of spotting talent and bringing it on. "We encourage people to grow. We don't see that sort of ambition as a bad thing," said Sir Richard, adding that the company saw training as a long-term programme rather than a quick fix.
Mr Ayling said that when he took over the helm at BA he was conscious - as a lawyer by training - that he was not as well rounded a manager as some of those who had been doing it all their working lives. As a result, he decided to watch and learn from a manager he had long admired: Sir Colin Marshall, the airline's chairman.
Now that he feels more comfortable in the role, Mr Ayling has extended the principle to all levels of the organisation. Drawing on his legal background, he is apt to refer to the company's management trainees as "articled clerks", assigning each one to work alongside a manager. The idea is that just as the law is largely learned by watching experienced people do it, so can management be.
Another theme to emerge from the discussions led by Sir Richard, Mr Ayling and Jeremy Strachan, director of legal and corporate affairs at Glaxo Wellcome (which followed up last year's second place in the Quality of Management Awards with third spot), was the ability to learn from others.
Mr Ayling explained how M&S's attention to detail was rubbing off on his colleagues, through the demands the retailer made of the airline in arranging for fresh produce to be carried from Kenya, or wherever, to the company's stores around Britain and many other parts of the world.
Similarly, M&S has long been renowned for raising the standards of suppliers by insisting on the best quality for its products.
On the tricky issue of reconciling this concern for people with the realities of restructuring a company, Sir Richard had less to say, since - with the exception of the streamlining of its head office in the Eighties - it has generally been able to avoid job losses. Any surplus in personnel resulting from such initiatives as the introduction of new technology had been swallowed up by opening new stores, he said.
At Glaxo, which has had to deal with an important merger in the past two years, and at BA, which has continuously responded to increased competition by reviewing its workforce, the keys are to act swiftly and to communicate clearly with employees. But Mr Ayling stressed that - no matter how obvious the business strategy - job losses were never easy to handle in practice because you are "dealing with people and their friends".
But perhaps the biggest factor behind such companies' continued success is a fear of failure, which, Mr Ayling admitted, amounted to paranoia. Like neurotic overachievers everywhere, they are conscious that they are only as good as their last year. Mr Strachan said, seemingly only half in jest, that the company would carry out a close examination to determine why they had slipped in the table this year, while Sir Richard was confident that if M&S were knocked off its perch next year, the headlines would read "What's Gone Wrong With M&S?"n