Leading article: From royal asset to national liability

To convinced republicans, the Duke of York's official role flying the flag for British companies abroad has always been ridiculous and demeaning for the country.

But to those who regarded the monarchy as, on balance, a benefit for Britain, it seemed to make sense to put royals such as Prince Andrew to some use. This was surely better than taxpayers paying for them to do nothing but cavort on yachts and shoot grouse. Rather an ambassador than a playboy, went the logic.

This newspaper has tended to lean towards the latter, pragmatic, view. If we are going to have a Royal Family, it makes sense to make them as useful as possible. But that was dependent on the royal ambassador in question upholding Britain's good reputation abroad. Revelations in recent days about the Prince's friendship with Jeffrey Epstein, a wealthy American financier who was convicted in 2008 of soliciting a minor for prostitution, have prompted even many normally enthusiastic royalists to question whether he is right for this job.

No one should be found guilty by association; not even a prince. But this thunderbolt did not come out of a clear blue sky. There have been complaints for several years about the lavish nature of the Prince's taxpayer-funded trips abroad to support British firms. He has been accused of using these missions to help sell his mansion in Surrey (which was eventually sold to a Kazakh billionaire for £3m more than the asking price). Last year the Prince's former wife Sarah, Duchess of York, was caught by a newspaper attempting to sell access to the trade ambassador to foreign businessmen. This track record means that the Prince does not have a huge store of goodwill to fall back on now.

Ministers, from the Foreign Secretary, William Hague, to the Business Secretary, Vince Cable, have been taking to the airwaves in recent days to emphasise what a good job the Prince has done for British companies. But there is no way of quantifying how much value he brings. Many of the trade deals would probably have been signed anyway.

In some ways, the Prince's defenders do have a point when they say he is being unfairly vilified. One of the criticisms of the Prince is that he has met Colonel Muammar Gaddafi's son, Saif, several times since 2007. But until very recently it was official government policy to hug the Libyan regime close. The Prince was merely doing what was expected of him. It would indeed be ridiculous to criticise Andrew for such connections while ignoring the policy set by both this Government and its predecessor.

Yet it would also be wrong to characterise the Prince as merely a harmless and innocent puppet. It was buried in last year's WikiLeaks blizzard, but one of the revelations from the leaked US embassy cables was that, in 2008, the Prince demanded a special briefing from the Serious Fraud Office over its investigation into BAE Systems, which was accused of paying bribes to secure the al-Yamamah arms deal with the Saudi Arabian government. The Prince later accused the SFO of "idiocy", in front of a senior US diplomat, for pursuing the case.

This was a scandal relating to something much more serious than the question of the Prince's unsavoury friends. This was an abuse of his position; an apparent attempt to interfere in the proper functioning of the rule of law.

An ambassador with a compromised reputation is ineffective; an ambassador who attempts to get involved in politics is positively dangerous. Prince Andrew seems to tick both boxes. And that means it is time for the Duke of York to march down the hill and out of official life.