The best medicine for Charles? Long walks at Birkhall, an end to his ban on lunch and... A daily dose of laughter, courtesy of Queen Camilla

SITTING on a bench in an eco-sanctuary, Charles is inspecting a reptile squatting in his hands. The world’s media surrounds him. But a passing bumblebee fancies some of the global limelight. It lands on Charles’s lap – perilously close to the then prince’s crown jewels, causing an understandable yelp of concern.

It’s a PR pratfall that would keep plenty of UK royal press secretaries awake at night. But sat next to Charles is Camilla, a pass master in defusing many a princely timebomb, using the best tool at her disposal: humour.

The then Duchess of Cornwall is consumed with giggles and the laughter proves infectious, spreading among the photographers and reporters and finally to Charles – and in the hubbub the bee buzzes off.

An inconsequential vignette from a 2015 royal tour perhaps, but one that reflects an essential facet of Charles and Camilla’s relationship and how they cope with problems large or small.

Deprived of late of glad royal tidings, the news that Charles is returning to public duties came as muchneeded balm, both to the House of Windsor and the British nation.

After treatment for an unspecified cancer, Charles on doctors’ advice, can attend events where he will meet people both indoors and outdoors. He and Camilla will visit a cancer treatment centre on Tuesday, while a state visit from Japan is planned for late June.

It will not be ‘a full summer programme’, but doctors are ‘sufficiently pleased with the progress made so far’ and ‘remain positive’.

To mark the announcement, Buckingham Palace issued a new photograph of King Charles and Queen Camilla, arms entwined and grins wide, taken in the palace’s garden the morning after their 19th wedding anniversary earlier this month.

If an ebullient portrait could paint a thousand words... for it is the monarch, eyes crinkling, looking longingly at his consort, rather than the other way around.

Camilla, meanwhile, holds her gaze outward, to the photographer,

symbolically encapsulating the duel roles she has played over the past few months. At 76, she has taken on more than a dozen extra engagements to keep the royal show on the road.

But it is the support she’s offered her husband in private moments of anguish that could prove a greater gift to him – and the Firm.

Nobody can chase away shadows – and bees – like Camilla, whose unerring knack of summoning the right quip at the right time never fails to lift her gloom-prone husband. Sometimes all that’s needed to set him off is a wry smile. She finds humour everywhere.

True, Charles has drawn comfort from other sources – steadfast public support, for instance. But as a source says: ‘Laughter is the key. They’ve got a very strong bond and a fantastic sense of humour.’

Since their early courtship, insiders say that Camilla has been adept at ‘keeping his spirits up’, and – as noted by Mail writer and royal biographer Robert Hardman – has continued to ‘inject a remedial note of levity’ over the years.

Delighted photographers have captured the pair in giggles on several occasions. In 2010, the couple laughed uncontrollably during an eccentric performance featuring a ‘cat organ’ at a festival held in London’s Clarence House.

The black-tied musician before them squeezed a row of toy cats, each emitting squeaks of varying pitches – and all a helpless Charles could do was to dab his eyes. Insiders also fondly remember Camilla’s cheeky interjection at last year’s Sandringham Flower Show, when she broke out in peals of laughter while examining a selection of pies.

‘That looks just like my husband’, she joked, beckoning aides towards an anthropomorphic bake with oversized ears and a crown.

Not satisfied, Camilla pulled Charles away from a serious chat with the show chairman to see ‘a very, very nice pastry’. As anticipated, Charles guffawed loudly. ‘It’s an artwork, I think,’ he said.

That first summer as King

Charles and Queen Camilla seems a world away from the events that would befall the Windsors. Following treatment for an enlarged prostate in January, the following month’s announcement that Charles had been diagnosed with a form of cancer and started ‘regular treatments’ shocked the world.

While a veil of privacy has been drawn over Charles – and the Princess of Wales who is also undergoing cancer treatment – a brief window into his progress was provided when he attended church at St George’s Chapel in Windsor on Easter Sunday.

Typically, Camilla kept close as he greeted crowds and laughed when a fan shouted out ‘Camilla is 17 now’ – causing momentary confusion, before pointing to her pet Cavalier. Knowing his wife would see the funny side, Charles retorted: ‘You’ll need a new one!’

In recent weeks, gardening and walking near their beloved Highland retreat of Birkhall on the Balmoral estate, where they spent their honeymoon in 2005, has been a remedial shared interest.

With its tartan walls, carpets and big open fires, Birkhall feels more like a normal house than a royal residence and is, says one source, ‘as close as it comes to being their marital home’.

‘This week at Birkhall has been particularly restorative for them both,’ a source told The Mail on Sunday. ‘They’ve had close friends staying that they’re deeply fond of,