Roger will dodge the question, but we'd love to know why

I have met quite a few millionaires, multimillionaires and billionaires over the years, and there is only one question worth asking them: why go on?

I have met quite a few millionaires, multimillionaires and billionaires over the years, and there is only one question worth asking them, really: why go on? After the first US$100 million (Dh367.3m), or $500m, or $1 billion, why not just put your feet up and call it a day? You already have wealth beyond the dreams of Croesus, let alone us ordinary mortals, so why not just enjoy it? The most satisfactory answer came from Philip Green, the self-made billionaire who made it from the rag trade to riches. "The amount of money I make is how I measure my success against my peers and my rivals. It shows me how good I am," he said. Candid and illuminating.

That response came back to me when I saw the news that Roger Jenkins, the 53-year-old tax specialist and investment banker well known in Gulf financial circles, was leaving Barclays to set up on his own. Mr Jenkins is said to have made anything between £40 million (Dh242.7m) and £75m last year at the bank, and has probably pulled in double-digit millions each year of the past five. The rich lists put his wealth at £120m. So why give up the day job and start out on his own?

Notoriously jealous of his privacy, Mr Jenkins did not elaborate on his motives. I chatted with a few City contacts on a short trip to the UK and found all sorts of possible explanations for his change of career. But most came back to that mix of money and ego displayed by Mr Green. "He wants to show he can make more than anybody else, more even than Barclays," said one astute business type. Mr Jenkins has undoubtedly done well in his 30-odd years in finance - most of it spent with Barclays - but the bank has also done well out of him. Most recently, he helped keep Barclays out of the clutches of the British government when he brokered a deal with Gulf investors that obviated the need for UK public funds, and the equity control that would have gone with that bailout, as happened at Royal Bank of Scotland and Lloyds-HBOS.

Barclays can count itself lucky that Mr Jenkins was talked out of quitting a year ago, as he apparently wished. Otherwise Marcus Agius, its chairman, might be reporting to the Treasury, rather than shareholders. And, in a neat twist a couple of months ago, Abu Dhabi sold its stake in Barclays, allaying fears that the bank might fall under the influence of such shareholders. So everybody is grateful to Mr Jenkins, including Abu Dhabi, which pocketed a multibillion profit on the deal.

Mr Jenkins is going to put those top-level Gulf contacts to good use in his new enterprise. He will be setting up an independent advisory business to advise sovereign wealth funds and other super-rich investors on how to minimise their tax liabilities on transnational deals. What Mr Jenkins - nicknamed "Roger the Dodger" - doesn't know about tax minimisation is not worth knowing. So that, apparently, is that. Mr Jenkins made the simple calculation that he could earn a lot more working for himself, with a stream of clients from China to the Gulf queuing up to take advantage of his expertise.

But maybe other factors played a part. Mr Jenkins's Bosnian-born wife, Dijana, is known to enjoy the high life of the Malibu set in California, counting George Clooney, Bono and Roberto Cavalli among their friends. Perhaps the tedium of working in the Square Mile, even with such a short commute from their London Mayfair home, wore them both down in the end. You cannot blame a man for wanting some time in the sun with his loved one, can you? With his own firm, Mr Jenkins can work wherever he wants, and Gulfstream to clients when needed, while Dijana can continue her philanthropic work from wherever.

City speculation suggested that other London-related factors also played a part. Mr Jenkins and Bob Diamond, the head of investment banking, are believed to be the two highest earners at Barclays, taking home much more than Mr Agius or his chief executive, John Varley. Perhaps the Barclays establishment saw some kind of threat in Mr Jenkins's cash generating ability and were privately relieved to get him out of the way?

Eye-watering remuneration such as this is not exactly in vogue in London at the moment, where the post-crisis spirit of austerity is threatening even those little corporate perks such as a day at Wimbledon or Lord's. Having him off the books might be a cosmetic nod in the direction of the governance lobby at Barclays, the conspiracists suggested. News of his departure came hard on the heels of a UK government initiative that would, among other measures, require greater disclosure of non-board members' remuneration. Absolute coincidence, I am certain.

Whatever the reasons, London's loss is the Gulf's gain. Mr Jenkins will set up offices in London, California and somewhere in the Gulf. You might imagine a beauty parade involving Dubai, Abu Dhabi, Qatar and Bahrain to secure his presence. His first project, it is said, is to help arrange tax-efficient Middle East backing for a new London-based hedge fund. His experience and expertise can only give added impetus to the financial expansion of Gulf institutions seeking to exploit investment opportunities among the bombed-out asset valuations of the West.

Along the way, Mr Jenkins will undoubtedly make an awful lot more money. But I would love to hear his answer to the simple question: why? [e-mail]