Like him or loathe him, Gordon Brown is the granddaddy of finance directors. His 10 years in the job as Chancellor of the Exchequer made him the longest serving finance minister since William Gladstone.

On June 28 he finally achieved promotion to the chief executive’ chair – the tallest one around the Cabinet table at 10 Downing Street.

After a decade of putting together the Government’s annual accounts and three-year expenditure plans, he had to start thinking about long-term strategy – President George HW Bush’s “vision thing”.

But he is not alone in making that transition. One in eight of FTSE 100 companies – 13 in total - is run by a CEO who used to fill the finance post.

On 6 October he completes his first 100 days as Prime Minister. What lessons can finance directors eying the top job take from Gordon Brown’s high-profile transition?

He could be forgiven for thinking the four Horseman of the Apocalypse had been waiting for him to assume the mantles of power.

First alleged al-Qaeda terrorists attempt to blow up central London and Glasgow airport. Then he finds himself in the middle of an old-fashioned Cold War diplomatic dispute with Russia.

The worst rainfall since 1789 brings misery to swaths of north England and the West Country. Finally foot and mouth disease returns to the UK for the first time in six years.

Six key lessons for aspiring CFOs emerged from his first seven weeks in 10 Downing Street.

The first is that a new CEO has to walk a tightrope between the need to stamp his or her own mark on the job and the desire not to upset the company’s stakeholders – investors, employees and customers – with any sudden changes.

This was particularly hard for Mr Brown who needed to put clear red water between himself and Tony Blair without being seen to disown the legacy of their decade-long reign over government policy.

The result was adherence to the major themes – military presence in Iraq, support for globalisation and a tough line of terrorism.

But he also made small but significant decisions, putting the “super-casino” on hold, launching a review into 24-hour drinking and starting a debate on the legal status of cannabis.

Murray Steele of Cranfield University School of Management admits he is surprised Mr Brown has pulled off the trick of changing the style of leadership without “slagging off” his predecessor.

“All the flamboyancy, showmanship and ego-centricity revolving around Tony Blair seems to have moved on,” he says. “One of the tricks Brown has pulled off is to distance himself from the past without being openly critical.”

The second is that the new CEO needs to have his own people in place beneath him. Brown succeeded in levering out key senior figures from the ancien regime such as Patricia Hewitt and John Reid without antagonising the rank and file or creating enemies within.

Jeremy Rickman, head of the European corporate officers practice at headhunters Russell Reynolds, says an ex-CFO needs bring on specialists in the skills he or she lacks. These typically include sales and marketing, and strategy.

Third, they must let go of their natural obsession with the numbers. Whether by choice of sheer force of events, the Prime Minister has managed to steer clear of his former brief, avoiding any mention of forecasts for the economy or the public finances.

Rickman says he or she should put a strong CFO in place to avoid being “dragged back” to the accounts.

Suzzane Wood, managing partner of the financial officers practice at Heidrick & Struggles, says it was important for Brown to choose someone – Alistair Darling – who would show the sort of loyalty he himself perhaps did not show to Blair.

Fourth, the new boss should show they are open to advice from all parts of the business. This was a particular challenge for Mr Brown, who had built up a reputation for working with a small coterie of advisers who blocked access for outside the Treasury.

By appointing as ministers or advisers Lord [Digby] Jones, former head of the CBI and a critic of Labour policies, former Metropolitan Police chief Lord Stevens and former Navy chief Sir Alan West, he showed he was willing to seek advice from a wider circle. “He has held proper Cabinet meetings which Blair never did,” Steele notes.

Fifth, new CEOs need their own strategy and agenda. In the PM’s case this came in the form of a mini-Queen’s Speech that laid out plans for energy, planning and transport.

According to Russell Reynolds’ Rickman, this is one of the toughest challenges for ex-CFOs.

“Analysts expect the CEO to be blue-sky thinker so a CFO has to move from being the sold, reliable feet-on-the-ground person. They have to convince the stakeholders they are the person who can come up with the strategy,” he says.

Lastly – and this is the most tricky – the new CEO must show “emotional intelligence” or an ability to build rapport with work colleagues and outsiders.

A fellow Scot, Steele fears this could be a challenge for a man who believes he is more intelligent that the people is working with – and working for.

So far these themes have served the chief executive well. He has turned a seven-point opinion poll deficit at the start of the year into a six-point lead while winning two by-elections.

Replace “opinion poll” with “share price” and “by-elections” with “product launches” and you see can why Brown headed for his holidays smiling – until foot and mouth hit.

However a week is a long time in politics and the UK’s new CEO may find the major challenges are still to come. Brown may have survived the first 50 days but management gurus will tell you it is the first six months that really count.

As Heidrick & Struggles’ Wood notes: “The first 100 days is important but this is a marathon not a sprint.”

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