Such a rule must be etched on the soul of Michael Grade, soon-to-be former chief executive of Channel Four Television and new executive chairman of First Leisure, the Blackpool Tower to bingo leisure conglomerate. Witness the sudden and dramatic resignation announcement from Channel Four on Monday, after a nine-year run which met with some initial scepticism but ended up drawing rave reviews. Then the mystery surrounding his destination: would he head a television consortium? Become chief executive of the Premier League? Or even Sam Chisholm's successor at BSkyB?
That's showbiz, folks. When Grade did appear on Wednesday at a hastily convened press conference at a City public relations firm, in a toned- down City suit, he had a clutch of television cameras in his face and assorted print journalists hanging on his every word. But did he leave them wanting more? You bet. "First Leisure is about selling tickets and getting people in the door," he said, but then refused to say whether he was just referring to the company's bingo halls or nightclubs, or to acquisitions yet to be made in the realms of sports and entertainment.
While the speculation rages over Grade's future, his reasons for leaving Channel Four are broadly clear. "I think he just got bored," says one colleague at the channel. "He became more and more detached from the day- to-day running by the political wrangles over the possible privatisation and the funding formula, and I think he also wanted to make a bit of money at the back end of his career through the kind of salary and options you can't get at a publicly owned broadcaster."
"I think what he's done is quite interesting and brave," says Greg Dyke, chairman of Pearson Television. "He's gone out to reinvent himself; he does not want to be one of those boring old men who've retired from television and get wheeled out to condemn their successors over a debate on the monarchy."
In returning to the world of profit and loss, of putting bums on seats or going broke, Grade is only following his genes. The Grades have never been shy of taking risks, and have always been able to capitalise on their inherent charm and showmanship to achieve their aims. As Lord (Lew) Grade, Michael's uncle, observes: "None of us Grades know how we came to do the things we did. Showbusiness came to us naturally, just like it comes naturally to Michael. I think somebody up there likes us."
It is an interesting reflection on the British business world that the Grade dynasty is viewed as a charming curiosity, rather than simply another Jewish family from Eastern Europe that has made it big running showbusiness. In Hollywood, such stories are two a penny.
In fact, the Grade family legend is as big as any in British showbusiness. Michael's father, Leslie Grade, was the theatrical agent who made his name booking stars such as Bob Hope, Danny Kaye and Jack Benny into London's bomb-damaged West End theatres just after the war, and running a successful talent business until a succession of strokes forced him to retire prematurely. The story goes that as a fresh-faced 17-year-old, Michael was sent to his first job, as a sports reporter on the Daily Mirror, in Leslie's Bentley. Michael ended up working there for six years, and took over his father's business in1966.
Leslie's brothers, Bernard Delfont and Lew Grade, were even more renowned. Lew founded ITC, the film and television company, in 1955 and went on to make such TV classics as The Saint, The Persuaders and The Muppets, and film epics such as Jesus of Nazareth. They would be shown on ITV via ATV, the company's independent television franchise in the Midlands, which during the Sixties and much of the Seventies was the most powerful ITV franchisee.
Lew's life peerage came in 1976, the same year as Bernard was ennobled, and marked the height of his powers. Then came the famous incident of Raise the Titanic, a film wholly financed by ITC which cost $30m, a fortune at the time for a film budget, and flopped spectacularly in every market except Japan. "It would have been cheaper to lower the Atlantic," Lew was said to have remarked afterwards. It set in motion a chain of events that deprived the company of its ITV franchise, and then forced its sale to the Australian tycoon Robert Holmes a Court. Lew left the company soon afterwards.
Bernard, meanwhile, made his name as a theatrical impresario, and hit the big time when he splashed out pounds 40,000 in the early Fifties to bring the glamorous showgirls of the Paris Folies Bergere revue to London. It ran for 2,000 performances and netted Bernard pounds 600,000 - enough to fund the Grade Organisation, a family talent agency cum theatre owner, which was eventually sold to EMI in 1967 for pounds 6m. Bernard joined EMI with the sale, and spent the next 11 years running the company's film and cinema interests, and for a short time was chief executive of the whole company.
When he was forced to retire in 1980, aged 70, he set about buying EMI's leisure and gambling interests, which by then had been sold to Trusthouse Forte. The subsequent buyout, in 1982, formed First Leisure Corporation, which he headed until his death in 1994.
All three brothers grew up in Stepney in the East End of London. Their parents, Olga and Isaac Winogradsky, were Ukrainian Jews fleeing the pogroms of the pre-Great War Russian empire, and on their arrival with their young family they set up in the rag trade. The children initially slept on the floor of the small house, and all left school at 14 to pursue careers in showbusiness. Lew and Bernard became professional Charleston dancers, both anglicising their names in the process - Bernard took the name Delfont at the suggestion of his agent so as not to get confused with his brother.
To say that the Grade family had character would be a gross understatement. There are so many stories and one-liners attributed to them that it would take a whole book to document them. Most are apocryphal. Bernard once ordered a salesman he was interviewing to sell him the jug of water on his desk; the salesman set the office bin on fire and said, "how much for the jug then". Lew was once at lunch with Leslie during their days as agents, when Leslie realised that he had left the office safe open. "Oh siddown," said Lew, "there's nothing to worry about. We're both here."
Bernard and Lew favoured outsize cigars ("if they are good enough for Churchill, they are good enough for me," Lew once remarked), and were champions of graft and salesmanship. Lew took particular pride in selling his ITC-produced miniseries to the American networks, while Bernard took particular pleasure in doing the deal to buy the Blackpool Tower for pounds 6m over a 4p cup of tea in Crewe railway station. At one point, during the Sixties, the power of the Grade family triumvirate was such that all angles of the Sunday Night at the Palladium show were covered. Bernard booked the acts; Leslie represented them; and Lew's company broadcast the show on ITV.
For Lew (now Lord Grade of Elstree), the sole surviving brother, the advancing years have not meant a reduction in graft or salesmanship. At 90, he is overseeing the post-production of Something To Believe In, a feature film about a terminally ill woman finding love with a troubled classical pianist in Italy, which he hopes will be in cinemas before the end of the year. He is also consultant to Polygram's film division.
He is particularly fulsome in his praise of nephew Michael, who he believes is the natural heir to the Grade name and dynasty. "Michael felt he couldn't do any more at Channel Four," Grade senior says. "At his age it's right to take another challenge - he could not stay there until he was 70.
"I'm very proud of Michael. He is the only person in the British entertainment business with creative ability and business ability. The two rarely go together."
Lew has supported Michael's decisions throughout his career, from his original move to LWT in the early Seventies to his sojourn in Hollywood where he produced a number of hit sitcoms for Embassy Television, including Who's The Boss, which ran in syndication for most of the decade. He even supported Michael when the latter decided to quit his $500,000-a-year Hollywood job to become director of programmes at BBC1 in 1984.
Michael's style - loud, red-socked and red-braced - never suited the BBC, with its Reithian principles and "all its corridors and closed doors", as he once remarked. Yet he gave the corporation Eastenders, consistently its most successful show in the past 10 years.
When, after John Birt, a former subordinate at LWT was appointed to be his boss, he left to join Channel Four, a similar culture clash occurred, with outgoing Channel Four head Jeremy Isaacs famously railing against the tabloid instincts of his successor. But his ability to charm both the talent and the politicians has meant that as his nine-year term comes to an end, the channel is perhaps in its strongest position yet.
Now, after 23 years in television, Michael Grade is turning his commercial talents to bingo halls, nightclubs and marinas. It sounds incongruous. But First Leisure is, and always has been (whatever Michael might say to try to placate its institutional investors) a Grade company. And despite his statement earlier last week that he would not be getting into the film business, or any other business outside the core competencies of First Leisure, there can be little doubt that his ambitions are not limited to collecting the takings from the bingo hall. For one thing, his favourite football club, Charlton Athletic, could use some of his commercial talents - and Channel Four could not exactly buy it.
So what will become of Michael's new career at First Leisure? Leave it to the ultimate closer, Lord Grade: "I don't know what he will do but you can bet it will be exciting. I think Bernard is up in heaven smiling and very happy. As for me, I'm just getting started. I've got two scripts that I want to produce after Something to Believe In, although one of them still needs some work ..."