Camilla's cheeky wink shows why the public has grown to love her

So the Duchess of Cornwall's wink has gone viral. In a spontaneous gesture of levity, as Prince Charles ushered President Trump and his wife from the room after they had had tea at Clarence House, Camilla turned to her protection officer, her face creasing into an enigmatic smile – and she winked. Now it is all over the internet.

What was she trying to communicate? It hardly seems to matter. In one flicker of an eyelid, the Duchess of Cornwall managed to diffuse any tension over President Trump's visit. And it seemed to encapsulate everything the nation has come to love about her. Although her pantomime playful plea may not have been the height of diplomacy, Camilla's lack of starchiness will have further cemented her status as a National Treasure.

That the Duchess of Cornwall is so at ease amid the pomp and pageantry, yet still respectfully negotiates the tightrope of protocol, is at the heart of her appeal. Unlike Prince Harry, scowling at Trump from a corner at an earlier reception in Buckingham Palace, Camilla's wink was guileless. As anyone who knows her will tell you, she has an enormous sense of humour. "She would have done it because it was amusing and a bit mad – that's her nature. Her whole family thinks everything is funny and none of them take anything too seriously. That is a Shand family trait," is how Nicky Haslam put it to me yesterday.

Camilla, once the subject of opprobrium, has warmed public opinion. Never bleating about her suffering, or seeking the limelight, she has shown herself to be the ideal consort for Charles. This is why he declared her "non negotiable". In the 40 years of their relationship, she has been his mainstay, embedding him with a greater inner security, while puncturing the excesses of his grandiosity. "She's made Charles so much better," another friend tells me. "And the Queen shares Camilla's sense of humour."

As the Duchess of Cornwall has relaxed into her role, she has proven herself to be a robust yet light-hearted asset, poised to handle any situation. Yet this has not come at the expense of her character. Unlike some of the younger royals who appear to be "in role" on public occasions, there is nothing arch or waxwork about Camilla. And certainly nothing precious.

She emanates ease, allowing us a sense of her true self. The American ambassador, Woody Johnson, correctly called her "a riot". While Jilly Cooper praises her thoroughly British bucolic nature: "When you stay with Camilla, she wanders about at breakfast in her dressing gown, wearing no make-up and her nail varnish is chipped."

Guests at Raymill, her country house that she escapes to for grounding sanity and unfettered time with her grandchildren, describe it as "all a bit chaotic, with sofas covered in dog hair." There's nothing grand about Camilla. She's not interested in status. Which is refreshing for someone married to the future King.

Her wink gave us a glimpse of her jolly hockey sticks whiff of naughtiness. Sometimes on official visits she's literally clutching herself as she tries to stem hopeless giggles or is openly rocking with laughter. Her sense of mirth is contagious. Let's hope that "Camilla's wink" becomes a byword for lightening up a strained situation, or just for a delicious moment of unguarded glee.