RUSSELL MYERS: 'I spent the week with Charles and Camilla - one thing is clear in their relationship'

The whirling , as flag waving locals jostle for position under the scorching afternoon sun. Dozens of serious looking security guards decked out in uniformed dark sunglasses and radio earpieces, seemingly fill every inch of space in between, meats and salty cheeses.

One group of middle aged women, who appear as though they are in fancy dress (I am later told they are not), have willingly queued up since 6am to be here. The scene of utter chaos wouldn’t be out of place in a Naked Gun comedy. But the principles at the centre of this mayhem are not paid actors, and a rather typical royal tour.

In the Piazza del Popolo, the central square of the stunning historic city of Ravenna, with its town hall at one end and former Papal ministry at the other, Charles and Camilla find themselves being ushered around a local farmers’ market. In a bid to keep up with the tide, one of their hosts, moving as quickstepped as Fred Astaire himself, shouts over: "We’re going this way!"

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Good luck, I think, considering it’s in completely the opposite direction to the tide of outstretched hands, hoping to have a brief audience with the royals. The couple, who this week celebrated their 20th wedding anniversary while in Italy and have of course seen it all before, are in a buoyant mood.

Camilla looks over to where I am standing with a dozen photographers' lenses locked in on her and gets the giggles. She gestures to her husband with eyebrows raised, as if to warn him to buckle up for the ride before a typically flamboyant Italian TV chef takes them round a pasta making stall.

On the final engagement on their four-day state visit to Italy, there is, true to form with this exuberant crowd, one last push before they jet back to Blighty.

Having travelled up from Rome that morning, they on-board a plush jet, me packed onto a dawn train for the two hour ride from the capital, Charles and Camilla squeeze in as much as they can to celebrate literary and artistic ties between our two nations. This tour has been all about collaboration after all.

It is the foundation of the King’s role as the invited head of state, forming the bedrock of his historic speech the day before at the Italian parliament, becoming the first British monarch to make such an address.

Aside from the box ticking of royal visits such as this, meetings with presidents, prime ministers and taking in the local sites, all of which have been navigated without fuss, it's warming to see two people who haven’t lost a sense of fun as well as the ridiculous.

In an interview with British newspapers accompanying Their Majesties this week, the Queen reflected on the secret to a happy marriage on their China anniversary.

It appears with everything going on in their life, from the King’s ongoing treatment for cancer, worries about his daughter-in-law after the Princess of Wales’ own diagnosis with the disease and the small issue of his estranged son Prince Harry and his various legal battles, laughter truly is the best medicine.

With typically self-deprecating humour at her pigeon Italian - confessing to only knowing the phrases “buongiorno” and “arrivederci” - for hello and goodbye - Camilla reminisced on their marriage of two decades.

"Twenty years, who could believe it was 20 years?" she says. "What is the secret? I don’t know. Well, I suppose it’s just sort of friendship, really. Laughing at the same things, getting on with life. I suppose doing this (on a royal tour) takes up most of the time."

It’s something I’ve witnessed first hand having travelled extensively with the King and Queen over the years and to which their closest aides admit is the foundation of not only their union but the monarchy at large.

One senior courtier tells me: "You can see it for yourself whenever they are together. They clearly enjoy each other’s company and have a real sense of mischief when things are as chaotic as they are on a royal tour.

"It’s the glue that holds them together and makes everyone’s jobs a little easier, knowing they are prepared to go with the flow. The King is determined to pack in as much as possible and the Queen not only knows how to be a supporting act, but to get the most out of her passions as well."

Indeed, as after visiting the tomb of the legendary medieval Italian poet, Dante – the "father of the Italian language", Camilla insisted on adding a trip to Lord Byron’s former home in Ravenna, telling how she was 'humbled' by the experience. Not wishing to arrive empty-handed, she even brought a collection of books from her successful ‘Queen’s Reading Room’ list and gave an impromptu speech after revealing a plaque.

She said: "This is just to say I never thought that my Reading Room would bring me to Ravenna and especially to Byron’s house. And I’m so pleased and so humbled to be here. It’s a really a great occasion."

Following her pilgrimage, John Mullan, a professor of English at University College London (UCL) speaking at the reception, praised her initiative, which has resulted in thousands more enjoying the pleasure of reading, adding: "It is an indispensable charity as children are increasingly dependent on screens."

At a time in their lives when their friends and peers are enjoying the fruits of their labour and more likely to be tending to their gardens than ramping up their working life, Charles and Camilla have entered possibly the busiest and most important era of their lives.

Their support for one another is key to their success. Whether it’s the Queen having to remind her husband to turn around for the cameras at the Colosseum, or helping him with important speeches before delivery. As one courtier told me: "They are as solid a double act as you will find."