Isabel Oakeshott is currently writing a book on the state of the armed forces with Lord Ashcroft.

Following a successful official visit to France, the Duke of Cambridge may have earned some respite from nagging questions over whether he represents good value for money.  His ill-judged decision to eschew the annual Commonwealth Day commemorations in favour of a laddish weekend on the ski slopes thrust an unflattering spotlight on how few public engagements he undertakes relative to his nonagenarian grandparents – but his ‘offensive de charme’ across the Channel is a reminder that he and the Duchess are powerful diplomatic assets.

During the coming months, Anglo-French relations will become more delicate and important than ever, not just because of the mighty influence of the French within the EU, but also because of our exceptionally close co-operation with them on matters of defence. Such is the current strength of our military ties with our Gallic cousins – underpinned by the 2010 “Lancaster House” treaties – that a French brigadier can be appointed deputy commander of a British military division, while a British officer can do the same within France’s first armoured division.

How joint planning and exercises will be affected by Brexit is yet to be seen, but is far more important to the future of UK national security than tariffs on brie and champagne.  That the Cambridges were able to dazzle La Republique last weekend without doing much more than the usual Royal routine of shaking hands, smiling munificently and generally looking the part indicates just how much they could do for this country in other parts of the world after the triggering of Article 50.

Now is the time for them to step forward, and do what (for all his undoubted talents) the rather less glamorous figure of Liam Fox, Secretary of State for International Trade, cannot do. This year and next, the couple should sally forth to our most promising prospective trading partners to convey the message that, so far from turning in herself, Britain is supremely confident about her future place in the world, and UK Plc is ready and eager to seize the opportunities presented by liberation from Brussels.

With only a fraction of the Duke and Duchess’ advantages, the King of Saudi Arabia has shown how it’s done. Accompanied by 1,500 flunkies, Salman bin Abdulazis Al Saud left nothing to chance when he embarked on a long tour of Asia earlier this month. His 459 tonnes of luggage, and the image of a gaggle of umbrella-toting manservants shielding him from the rain, were a source of widespread western amusement, but few are laughing at the multi-billion pound trade deals apparently generated by the 81-year-old’s trip. The Saudi monarch is said to have delivered business deals worth at least $90 billion during his tour, with more expected. In America, his reformist son, Deputy Crown Prince Mohammad bin Salman, came back from a meeting Donald Trump with a $200 billion investment deal in his back pocket.

Nobody is suggesting that the Cambridges dirty their hands by personally engaging in trade or business negotiations. That would fatally undermine their position. But what they can do is lay the ground for others to do this work, both by generating goodwill overseas and projecting soft power, on which (as our capacity for the hard variety diminishes) both the FCO and Ministry of Defence are increasingly keen. This summer, the couple are already scheduled to travel to Germany, our premier European trading partner; and Poland, one of the fastest developing countries in the EU; this summer. Dozens of other destinations should be added to their 2017 and 2018 itinerary.
Few countries have royal families who undertake such international tours. King Salman’s has now ended. Whilst the domestic reputation of our Royals would not recover from emulating the Saudi monarch’s extravagant style, his experience offers some useful insights.

His 18-day trip has taken in Malaysia, Brunei, Indonesia, Japan and finished in China. And in Asia the absurd size of his entourage, far from inviting ridicule, projected an image of power, and delivered a strong message that Saudi Arabia cares for its bilateral relations with hosting countries. Nowhere was this more evident than in Jakarta, where tens of thousands of Indonesians lined the streets waving Saudi flags in the pouring rain.

Like the UK, Saudi Arabia is undergoing a transformation of its own, albeit one that is social-economic rather than political. The world’s biggest exporter of oil is implementing a radical restructuring of its economy for a post-oil era. Key to this programme is greater international trade, more foreign direct investment into Saudi, and skill transfer to support the creation of new sectors.

As the deepening instability in the Middle East and the change of White House occupant render European and US commitment to the region less certain, the Saudis have identified the major Asian economies as their most promising potential partners. The strategy appears to be paying off. In Indonesia, the two governments agreed to a $6 billion joint venture between their state oil companies, Aramco and Pertamina. This was followed by an Aramco deal to invest $7 billion in a Malaysian oil company.

In Japan, high-level discussions were held concerning a potential listing on the Tokyo Stock Exchange for the highly-anticipated $100 billlion Aramco IPO, and a deal was signed for the creation of a special economic zone in Saudi.  In China, some $65 billion worth of deals had been signed by the time the King’s meetings in Beijing came to an end, continuing a trend that has seen trade between the two countries rocket by 7500 per cent since 1990, from $1.2 billion to $75 billion in 2016.

As the Duke gives up his 20 hour a week job as an East Anglia Air Ambulance pilot and prepares to move to Kensington Palace full time, palace officials and the Foreign Office will be giving careful thought as to the positive role he and his wife might play at this most sensitive and exciting time. Sources close to the Duke have been briefing that he is far more eager than he appears to embrace the responsibilities associated with being a full time member of the Royal Family, and second in line to the throne.

At all costs, he must not morph into his embarrassing uncle “Air Miles Andrew”, grubbing around with Kazakh oligarchs and convicted sex offenders. The Duke of York’s record as a roving trade ambassador, brought to a sorry end in 2011, at least shows how it’s not done. But within clear and appropriate boundaries, there is every reason for the Duke of Cambridge to set forth into the world and do his bit to help make Brexit an economic success. We may jeer at his “dad dancing”, and sniff at his high-fiving with blonde models – but, overseas, he and his wife retain a powerful allure. Now is the time to make the most of this unique asset.