With David Cameron in Saudi Arabia for his first visit since becoming Prime Minister, it is difficult to avoid the sense of the British Government once again holding its moral nose in the interests of our commercial and political influence.

As uncertainty rocks regimes across the Arab world, it is a game that is becoming even more difficult to play. And the moral trade-offs only look more squalid than ever.

There is little that can be said in favour of the Saudi Government. It is a stern autocracy that remains single-mindedly dedicated to the survival in power of its hereditary ruling elite and has, for 50 years, exported an obnoxiously intolerant version of Islam around the world. Indeed, in terms of its power structure, there is little to choose between the House of Saud and the repressive regimes tottering and falling across the Arab world.

Britain's long historical relationship with Saud Arabia has yielded no discernible influence on its abysmal human rights record. This is a country without political parties or elections, where the constitution is the Koran, and medieval, sharia-inspired punishments include stoning, amputation and lashing; where a proposal to lift the ban on women driving elicited a report by the nation's highest religious body warning that there would be "no more virgins" if the ban were lifted, and that men and women would resort to homosexuality and pornography; where a 34-year-old woman who defied the ban was sentenced to 10 lashes while another was recently beheaded for practising sorcery.

It is difficult, therefore, to build a plausible moral justification for Mr Cameron's trip to Riyadh to meet King Abdullah and Crown Prince Nayef. Trickier still given that his primary task is to persuade them to buy Hawk jets, training aircraft and all kinds of other British-made military technology.

That said, it is as well to weigh the economic realities of Britain's defence industry, which accounts for several hundred thousand highly skilled jobs and a good slug of our much-needed manufacturing base. Indeed, there is a tacit understanding of these things in Parliament. The cross-party Committee on Arms Export Controls may have queried mildly why we were still licensing arms exports to the kingdom "given there was some unrest", but such grumbling remains largely below the political radar. There are also political concerns at stake. With Saddam Hussein long gone, the argument goes, the Saudis are the region's last remaining bulwark.

Ultimately, for all the unpleasantness of the regime in Riyadh, Mr Cameron is unlikely to suffer any lasting damage from his one-day visit there. After all, in November he led Britain's largest-ever business delegation to China, a country with a human rights record if anything even patchier than that of Saudi Arabia.

But if it is too much to expect moral consistency from our Government's foreign policy, we can at least ask Mr Cameron and his Foreign Secretary, William Hague, to reassure us that they are aware that the sands of Arabia are continuing to shift in highly unpredictable ways. So far, the region's monarchies have survived the uprisings of the Arab Spring better than the other tyrannies. But while Morocco's King Mohammed has bought off much of the protest movement with reforms, the Saudi elite has barely responded at all. They will not get away with it for ever. The time for the people of Saudi Arabia to make their voices heard cannot be far off. And when they do, it will take some fancy footwork for Britain to come out on the right side.