Corporate cultures are very hard to define, which is probably why so many consultants make so much money advising on them. Different companies obviously have different cultures. At Virgin nobody wears a tie, at Google nobody wears shoes but at a City law firm it is suits and ties or go home and change.

But more important differences, such as the approach to business ethics, are harder to describe, and harder to change.

This is the challenge facing Dick Olver as chairman of BAE Systems, Europe's largest defence company. BAE has been battered by allegations of bribery and corruption in its arms sales which are seriously damaging its international reputation.

The High Court's ruling yesterday that the Serious Fraud Office acted unlawfully in halting its investigation into BAE's dealings with Saudi Arabia rakes up corruption allegations once again.

BAE was not a party to the case that ended yesterday but it did lobby the Government to shut down the SFO inquiry and cannot, therefore, pretend to have nothing to do with it. Now the company must wait to see if the SFO decides that yesterday's judgment means it must reopen its investigation into allegations of slush funds, payments to middlemen and bribes to Saudi princes.

The possibility that the SFO investigation could be restarted threatens BAE's £20 billion deal to supply Saudi Arabia with 72 Eurofighter Typhoons. BAE has made £43 billion from the Saudis so far and if the Typhoon deal collapses it will leave a nasty hole in the company's future profits.

BAE continues to deny any ethical wrongdoing in its past defence deals. But sometimes vigorous denials are not enough.

Mr Olver believes that BAE needs a cultural revolution. He has asked Lord Woolf, the former chief justice, to investigate the company's ethical processes and make a public report, which is expected soon. Mike Turner, BAE's chief executive, has bought into this campaign of reform but Mr Turner is a product of the old regime. The need for new blood and new ideas is the main reason that there is understood to be only one internal candidate to replace Mr Turner when he retires in August.

Moreover, some BAE insiders question whether that single internal candidate, Ian King, is the right man to force through cultural change across a multi-national organisation employing 96,000 people.

As a result, the odds on an external candidate are shortening. BAE may even get its first non-Brit.

Mr Olver will hope that the Woolf report will draw a line under previous ethical failings and provide the new chief executive with a blueprint for cultural change.

Such efforts can make a difference. Chuck Prince's famous “five point plan” to improve the ethical culture at Citigroup appears to have had some success although, of course, ethics turned out to be the least of Citi's problems.

But it will not be easy for the new BAE chief. The company still faces investigation by the SFO into allegations of corruption in four of its international arms deals. The US Department of Justice is also examining the company.

Attempts to reshape the company's culture risk being undermined by a constant drip, drip of bad news from the array of investigations.

The new chief executive may find himself fending off so many allegations of past ethical failings that he struggles to talk credibly about the future.

But that task, so vital to the future of Britain's biggest manufacturing company, would surely be easier for an outsider.

david.wighton@thetimes.co.uk

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