As fading stars go, Brown shows a flash of good timing

An old showbiz maxim states simply: "Always leave 'em laughing." These four simple words, coined in 1903 by the American lyricist George M Cohan, are worth heeding for comedians and anyone else in the public view. The logic of such sentiments is crushingly simple: quit while your fans are wondering why you didn't stay longer, rather than why you didn't depart sooner.

The trouble is, like most advice, it's easier to give than to apply. Once addicted to life in the spotlight, it's not so easy to know when to get out, which is why so many in both entertainment and politics fatally outstay their welcome. One politician at least took Cohan's words to heart last week. Having seen the premiership of the UK government slip from his grasp in the days following the general election, Gordon Brown's departure from both 10 Downing Street and the leadership of his party was as decisive and elegant a gesture as any he's made.

With evening closing in, and his wife and two young sons by his side, he stood in front of the famous old black door for the last time, thanked the country, bade us farewell, and strolled away, quite literally, into the sunset. Meanwhile, across London at the massive 02 Arena (imagine an aircraft hanger with attached coffee bars), others who are old enough to know better were showing altogether less judgement. Even as Mr Brown was packing his bags, the Hollywood superstar and musical icon Julie Andrews was demonstrating the brutal consequence of ignoring Cohan's simple phrase.

No one doubts that Ms Andrews is a true giant of the silver screen. From Mary Poppins to Thoroughly Modern Millie, her career has included a number of unforgettable musical performances. Indeed, her appearance during the opening credits of The Sound of Music, whirling like a spinning top on that grassy hillock before unfolding that astonishing bell-like voice of hers, remains a defining moment of movie history.

Ms Andrews may still look a million dollars, but her once-pristine vocal cords are shot through, the result of a serious throat illness and botched operation in the 1990s. Nonetheless, this 74-year-old national treasure booked herself in at London's largest entertainment arena and charged punters up to $200 (Dh735) per seat to witness what was advertised by Ms Andrews's manager as "a beautiful woven blend of her singing along with her guest stars".

In fact, it proved to be anything but. During the entire concert she "sung" (if that's the right word) only three numbers. With ticket receipts reportedly exceeding $1.5 million, that works out at about $2,000 a word. Disgruntled fans fled in huge numbers well before the end of the gig, and some are now claiming a full refund. As one blogger who had been in the audience commented online the next day: "The trouble with top-notch performers is they can't bear to let go."

What on earth provoked this star to appear at a venue in which anything less than the massed bands of the Grenadier Guards would struggle to make an impression? The answer is, of course, a reluctance to admit to the inevitable passage of time. Yet Ms Andrews is only the latest of a stream of living legends who have ignored Cohan's brief homily at their peril. Last month the pop singer Whitney Houston suffered a similar debacle in the same venue. Ms Houston may be famous for her rendering of I Will Always Love You, but by the end of her calamitous gig even her most loyal fans were struggling to reciprocate her sentiment.

Thankfully Mr Brown at least knew how to leave us laughing. "Thank you, and goodbye" were his last words before he vanished from both our TV screens and public office. What's more, his grin as he made his final farewells seemed, for once, genuine. And well it might be. For a man who has climbed every mountain during his 14 years at the top, he had nothing left to prove. Cohan achieved immortality with a statue in Times Square. Whether Mr Brown will gain a similar honour in Parliament Square is unlikely, but the grace he showed once his time was up will have done his chances no harm. As to whether he might be persuaded to return to the spotlight any time in the future, only time will answer. I wouldn't bet on it. Ageing showbiz stars, please take note. Michael Simkins is a writer and actor based in London.