They also visited the King’s Foundation Curious Garden, which aims to encourage people to get curious about gardening.

Charles was seen chatting with Sir David Beckham and broadcaster Alan Titchmarsh, with whom he created the garden, as well as other celebrities, like Dame Judi Dench.

But he was also seen interacting with a pooch at the Animal and Plant Health Agency’s “scents and sensors” exhibit, which caught people’s attention.

The exhibit explores how detection dogs and technologies can help to combat plant pests and diseases.

Charles met Zinc, a three-and-a-half-year-old cocker spaniel trained to detect plant diseases.

He was pictured playfully stroking the dog.

Alongside his trainer, Luke Jones, Zinc demonstrated how quickly he could locate a toy he had been trained to smell, showcasing his advanced sense of smell for identifying diseases.

The King asked Mr Jones about Zinc’s speciality: “This one only specialises in this?”

Mr Jones told him Zinc is a specialist in sniffing out Phytophthora, a group of fungus-like organisms that cause crop losses around the world.

The Duke and Duchess of Edinburgh, The Princess Royal and The Duke and Duchess of Gloucester separately toured the show on Monday evening.

This year’s event features show gardens containing such items as a Barbara Hepworth sculpture to Japanese bonsai trees.