King Charles steps out for surprise appointment as Harry looks at ease

There was an unexpected patient waiting for King Charles and Queen Camilla during their visit to London Zoo on Thursday.

The couple found themselves crouched beside Lannister, a Humboldt penguin, as they joined zoo veterinarian Stefan Saverimuttu for a routine health check.

Charles appears in celebratory mood during the visit, which comes amid Harry's special engagement in Birmingham.

Rebecca English shared a video on Instagram showing the King and Queen carefully listening to the heartbeat with with colourful stethoscopes.

King Charles used a red one, while Queen Camilla carried out her own examination with a blue instrument as the calm bird perched patiently on a rock.

Their visit formed part of celebrations of the 200th anniversary of the Zoological Society of London (ZSL), with the royals spending time learning about the charity's conservation work and meeting some of the zoo's best-loved residents.

Vet Stefan Saverimuttu said Lannister had been the perfect patient.

"Lannister sounded perfect and Lannister was very well behaved for the King and the Queen," he said.

He also praised their confidence saying: "Both of them were really enthusiastic about them."

Penguins have quite a beak, so if you've never met one before they can be a little intimidating, but neither the King nor the Queen was intimidated in the slightest.

They went straight in, gave it a go, and they did really well.

King Charles smiled as he described the penguins as "very endearing." He also met Polly, a Galápagos tortoise, and offered her a few snacks.

When Polly appeared unimpressed by the the monarch’s offering, Charles jokingly asked her keeper if the tortoise was on a "diet.”