AS the applause began, Giorgio Armani stepped on to the Milan catwalk last week, shook hands with Spanish actor and dancer Joaquin Cortes, who was sitting among the celebrities in the front row, and waved to the crowd at his autumn/ winter menswear show. Tomorrow he will soak up the adulation at his first women’s couture collection in Paris.

The designer has every reason to smile. This year it will be 30 years since he sold his Volkswagen Beetle to pay for material to produce his first collection. He has turned that £500 investment into a £2 billion, 300-shop, 5,000-employee global empire and become the most successful designer in the £10 billion world- wide fashion industry.

But behind the scenes in Milan last week the only man in town “wearing himself” looked nervous. His nut-brown face was tight and his eyes darted nervously around his office and design studio. Armani is facing the toughest choice of his career. He has a date with destiny.

It may be 30 years since he founded his business but he was a late starter. Now he has just turned 70. In an industry where you are considered old at 40 — Gucci’s superstar designer Tom Ford quit recently, aged 42 — what everyone wants to know is: can the one-man brand play on?

Armani has no children and, therefore, no natural heir. He has no deputy and has not anointed an in-house successor. He is chairman, chief executive, chief designer and sole shareholder of his vast business. When will he retire and what will happen after he quits?

“Quit?” Armani said last week, throwing back his head and laughing. “Why does everyone want to send me to a retirement home?”

In an exclusive 30th anniversary interview with The Sunday Times, he said: “I can’t put a date on retirement. It could be in the year 3000. I feel young and I am someone who believes in modernism. I am somewhat driven and always ready to embrace new opportunities.”

Armani believes he has got what it takes to go on for at least another decade. “I have not fallen into the trap of becoming ridiculous. I have not had a facelift. I do not dye my hair. I take care to dress my age. Unless I suddenly fall ill, I cannot imagine giving up a part of my company or handing it over to somebody else.”

The idea of an 80-year-old on the catwalk may sound preposterous. It will certainly alarm industry observers who say that, by delaying his succession, Armani risks weakening his brand. Nigel Nicholson of London Business School said: “It is common for heads of family businesses not to think about the future, to think they are immortal, but this does not serve business interests.”

He may not be immortal, but Armani is nothing if not fashion’s great survivor. His rivals — Yves St Laurent, Calvin Klein, Donna Karan, Valentino Garavani and Gianfranco Ferré — quit their front-line design roles years ago, but he remains at the helm of a company that announces record results almost every year.

The firm’s most recent figures show that group sales in the first half of 2004 were up 8% to €644m (£448m) compared with the same period a year earlier. Pre-tax profits rose 23% to €89m. Net cash reserves stand at some £150m. Armani is one of only three Italian companies in the list of the top 100 global brands, drawn up by the analyst Interbrand.

Few would bet against Armani continuing for another five years at least. Indeed, the older he gets, the harder and faster he seems to be working, searching for new areas to conquer.

There is tomorrow’s debut couture show in Paris. He has just opened the largest fashion store in China. Next month work will begin on the first of 14 Armani hotels — a £750m joint venture with the Dubai property group Emaar.