Leading article: Sweeteners and slush funds in a complex world

Moral indignation is in ready supply over the revelation that the UK's biggest arms dealer, BAE Systems, paid £1bn over the past 10 years to the Saudi prince who brokered a deal which saw Britain sell £40bn of warplanes to Saudi Arabia. There is talk of slush funds, bribes, corrupt payments and sweeteners. We are even told that the portly prince at the centre of the storm is "cigar-smoking", as if such corrupt, capitalist cartoon detail were the final, clinching proof. How can we lecture Africa about corruption, it is asked, when we practise it ourselves on this scale?

It is, however, more complicated than that. All payments made were written into the contract and known to the UK and Saudi governments, so it is unclear exactly who was deceived. Nor is the secrecy surrounding the deal any stricter than the confidentiality routinely imposed on commercial business deals sealed around the world every day, in which commissions are customarily paid to agents and intermediaries.

Then there is the nature of a Saudi kingdom run by royal princes, where the lines between state and personal expenditure are not so well-defined as in the West. Investigators found there is little distinction between official government bank accounts and those of the royal family. One set of payments went into an account to pay the expenses of the private Airbus of the arms broker, Prince Bandar, but since he was for almost three decades the Saudi ambassador to the US, and is now head of the country's national security council, the line between flights for personal and state activities was often blurred.

Corruption is a plague in much of the modern world. We have leverage in insisting that it must be combated most particularly where, as in Africa, we have concern that our aid monies could be misused. But that is less the case in Saudi Arabia, which is not in poverty, does not receive our aid, and where we do not have the same leverage in imposing western values of democracy, accountability and open governance.

Saudi Arabia is not an attractive place, with its princely privilege and its fundamental Wahhabism, which is the source, and funding, of much of the violent Islamist ideology in our times; most of the 9/11 hijackers were Saudi nationals. For all that, it has value as a strategic ally: Saudi Tornados flew alongside RAF bombers in the first Gulf War; Prince Bandar was the man who indicated that Saudi Arabia would increase oil production when a recent oil-price rise loomed; he is said to have been the man behind the Mecca agreement between Fatah and Hamas for the establishment of a Palestinian unity government.

All this is not to make excuses. And the Attorney General was quite wrong to stop the Serious Fraud Office investigation into the affair. But it behoves us to take on board the complexity of the situation. It may well be that something unseemly has gone on between BAE and the Saudis. It raises suspicions that the payments to Prince Bandar are not listed as commissions but as "quasi-official fees for marketing services" which sounds obfuscatory, if not downright dissembling. But assumptions of guilt in ignorance of the full facts are not helpful.

There is a lot at stake here, in Middle Eastern politics, in combating worldwide jihadist violence and in the £20bn deal for the sale of Typhoon jets which BAE is due to sign with the Saudis next week, and on which thousands of jobs turn. Simplistic moralising is not what is required here. The Government has a duty to scrutinise this deal and spell out why the payments made are merely unconventional, rather than corrupt. If it does not do that, a pall of suspicion will linger, which can only damage British interests in an altogether different way.