London (CNN) -- Royal tours don't come cheap, especially when they involve traveling to the other side of the world.
The Duke and Duchess of Cambridge are making their way through four countries in little over a week.
They're taking in all sorts of sights including the skyscrapers of Singapore, the jungles of Borneo and an island paradise in The Solomon Islands. It's fast, furious and at times fun. But it's also part of a high stakes mission to retain Britain's position on the world stage.
Catherine and William are traveling with a small team including a David Manning, a key adviser and former British Ambassador.
On the ground they also have backup from local diplomatic missions. The costs of (scheduled) flights and security alone will easily go into six figures, and most of this expense will be met by the British taxpayers.
So how does the Foreign Office justify the outlay, especially in an era of fierce public spending cuts? Well, they see it as an investment.
The couple is representing the queen on this tour; they are promoting their own interests, such as conservation and hospice care; but they are also promoting British interests.
In Singapore they called on the prime minister and president. The photo opportunity looked like it could be a bilateral meeting of political leaders but without the politics, so it was all smiles, which makes for a more appealing picture.
The duke and duchess visited a Rolls Royce engine factory in Singapore. William talked about the country being a hub for British businesses operating in Asia: "British business now has some £25 billion ($40B) invested here -- a massive vote of confidence in this dynamic country." It reads like a pamphlet from UK Trade & Investment (UKTI) -- the body responsible for promoting British business abroad.
The difference between a UKTI pamphlet and a Prince William speech is in the audience numbers. Unlike the pamphlet, William's speech appeared across the world's media and Catherine provided an accompanying photo opportunity by flexing her biceps in front of a vast aircraft engine.
Rolls Royce can't buy that kind of publicity and the British government knows it. Specifically it is the young royals -- Catherine, William and Harry -- who have the power to draw this kind of attention. The other royals just don't hold the same interest. Did you even know that William's uncle and aunt, The Earl and Countess of Wessex, are on their own tour of Canada right now?
Catherine and William did more to promote UK Inc. in Malaysia, all under the watchful gaze of a vast media press pack. All the major local, Australian, U.S. and UK TV networks are following their every move, as are print reporters from across the planet.
Meanwhile, the great and the good are queuing up to rub shoulders with the golden couple, which itself presents the Brits with a unique networking opportunity.
Royals have always had a diplomatic role. In Britain, they used to hold absolute power but these days they work with government to provide soft power abroad.
There are discussions currently under way to bring the royals to crucial emerging markets like China, India and Russia. You can't put a price on such royal missions, but the British government have, in Catherine and William, found a unique vehicle to promote national interests, and they are making the most of it.