Royal Rota: King Charles-to-be and what's Brexit got to do with him anyhow?

I’m sitting at RAF Brize Norton on board the military refuelling plane that these days doubles up as an executive jet for the Prime Minister and members of the Royal Family.

Brize Norton is a busy place, it’s the RAF’s Heathrow airport, and while we await the arrival of the Prince of Wales, I wonder if this airfield could be the solution to Heathrow’s expansion problems: there aren’t tens of thousands of people living under the flightpath, no M25 getting in the way of a longer runway, no marginal constituencies nearby in rural Oxfordshire.

But the area is still home to David Cameron and I can imagine he and Samantha would be out with their placards in the nearby town of Witney should such a plan ever be proposed.

It’s Brexit Day today (Theresa May is triggering Article 50) and our royal passenger is off to press some flesh in the EU.

Prince Charles is embarking on a tour of three European countries: Romania, Italy, Austria.

The prince lays a wreath at the Tomb of the Unknown Soldier in Bucharest Credit: PA

These trips are organised in consultation with the Foreign Office, and the Foreign Office thinks our Royal Family are a pretty useful bunch right now, when it comes to promoting the UK abroad.

So yes, the Prince will indulge in visits and themes in Romania which are close to his own heart: preservation of traditional skills in agriculture, creating wetlands for wildlife in cities, seeing Romanian village life.

And in Italy, he will meet the Pope, tour a town hit by an earthquake last summer, and raise awareness of his campaign to promote the use of wool as a natural fibre.

So far, so very Prince Charles you might say.

But there is a wider purpose here which applies to all three EU countries he is visiting.

The Prince of Wales and the President of Romania Klaus Iohannis at the Palace of the Parliament in Bucharest Credit: ITV News

In the week that Theresa May formally tells the EU that we’re off, the Prince, who will be joined from Italy onwards by his wife the Duchess of Cornwall, will be conducting some soft diplomacy on Brexit.

The message the Foreign Office wants to go out loud and clear in these particular countries is that the UK is ‘leaving the EU but we’re not leaving Europe.’

So, there are opportunities for the royal couple to talk about Britain’s past contributions to Europe (marking the centenary of British forces entering World War I on the Italian/Austrian front) as well as Britain’s current contributions (Romania only has hospices for the dying because the UK introduced the whole concept to the country) and our future contributions to religious tolerance in Europe (the Prince and Duchess will meet the Pope and tour the Vatican).

But this royal couple does not have the same celebrity image that Princes William and Harry enjoy.

The Prince of Wales, who is on a nine-day tour in Europe, will be joined by the Duchess of Cornwall Credit: PA

And so on board my RAF Voyager to Bucharest, there are many fewer photographers and journalists.

Demand for pictures of - and interest in - the work of The Prince of Wales and the Duchess of Cornwall is much lower.

But we should never forget that Prince Charles is effectively our ‘king-in-waiting’ now that his mother has cut her workload and no longer travels abroad.

And he will one day be the King with Camilla, in all likelihood, the Queen (as his consort).

We’re witnessing a very slow and gradual transformation from one Monarch to the next – the exact opposite to what the country witnessed in 1952 when King George VI died suddenly one February night while the then Princess Elizabeth was in Kenya.

And the more we can understand this 68-year-old now, the better we will understand the new King when the time comes.