CFOs around the world are looking on in a mixture of admiration and jealousy at the success of a former member of the ranks. Tidjane Thiam, CEO of the U.K.'s Prudential PLC is in the process of trying to pull together what must be the biggest deal of his life. The potential $35 billion takeover of AIA will at a stroke convert the company from a rather staid UK life insurer into a fast growing Asian financial services behemoth.

This is not the way that text books say it should happen. Generally when a CFO is elevated to the CEO position - as happened to Thiam in the middle of last year - it is usually because there is some dreadful financial crisis looming that only an experienced CFO can really manage. Indeed the promotion of the CFO to the CEO position is likely an admission that there will not be any major strategic moves, rather a relentless of pursuit of cash, debt repayments and risk hedging.

What makes Thiam's move even more remarkable is that it was reported that he tried to scupper the plans of his predecessor Mark Tucker when he was thinking of making a bid for AIA a year ago. Cynics might say that he wanted to do the deal himself.

Other ex-CFOs of banks, who now find themselves in the top seat, could be forgiven for feeling pangs of jealousy at what Thiam is trying to do. For instance, Steven Hester, the CEO of RBS is the ex-CFO of Credit Suisse. His job is now all about finding ways to offloads toxic assets, keep bankers from leaving and trying to explain to a furious public why bankers need to be paid even if the bank makes a loss. How much more fun to throw the whole institution at a deal that will not only define a decade but see you transform the geographic and growth profile of the business. Thiam is reportedly looking at a Hong Kong listing post deal and will probably have to move to Asia personally.

The trend of promoting CFOs to CEOs is only around 15 years old and can be partly attributed to the private equity business. Once companies are bought out by PE firms, the first priority is to manage the financials as tightly as possible, paying down the acquisition debt and serving interest before arranging an exit. This placed great emphasis on financial skills as opposed to strategic vision. Just such a situation happened last week when Carlyle led a group of investors in a $550 million deal buying into Bank of Butterfield in Bermuda. In the process, the existing CEO Alan Thompson left the bank. His successor? Bradford Kopp, the CFO.

The promotion of the CFO to the top spot can be seen as an admission that all the focus will be on the balance sheet and not the P&L account. That could explain why CFOs at Goldman Sachs and HSBC - David Viniar and Douglas Flint respectively - tend not to be mentioned as the next CEOs of the banks; these institutions have very strong internal strategic cultures matched by fortress balance sheets. An admission that either is needed in the top spot would be a sign both of a weak culture and balance sheet. But with Thiam now pioneering the way, it can be shown that CFO's can make great strategic CEOs. Who will be next?