Like most married couples, Prince William and Kate Middleton have a well-rehearsed secret code that they often use to subtly communicate during public outings.

This sweet covert language was spotted in a rare heartwarming moment shared between the Prince and Princess of Wales during a German state visit on December 3, as the pair viewed artefacts from the Royal Collection at Windsor Castle.

As the loved-up couple gazed at the several items on display in the Green Drawing Room, Kate, 43, was seen holding an animated conversation with one of the curators.

But while her husband initially appeared captivated by their brief chat, he soon spotted that his uncle, the Duke of Edinburgh, was moving towards their table.

And so in a quick bid to prompt his wife to move on to the next set of items, William, 43, placed a delicate hand on Kate’s back – a subtle signal that it was time to wrap up their conversation.

Fortunately, Kate clearly sensed William’s restlessness from the secret code and they both soon issued a heartfelt ‘thank you’ before walking away.

The special exhibit at Windsor Castle was one of several events to welcome President Frank-Walter Steinmeir and his wife Elke Budenbender to the UK, culminating in a festive state banquet held inside St George’s Hall.

And it was certainly Kate who stole the show that evening. The princess gleamed as she arrived at the glitzy event in a sweeping pale blue Jenny Packham gown while her hair was delicately crowned with Queen Victoria’s rare Oriental Circlet tiara.

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The Prince and Princess of Wales viewed artefacts from the Royal Collection at Windsor Castle during a state visit from the German president on December 3 – with their secret royal code captured by eagle-eyed onlookers

While Kate has often stunned royal onlookers with her highly personable nature and innate charm, her tendency to engage in lengthy conversations with the public during walkabouts has occasionally been to her detriment.

The rules related to greeting members of the public are not set-in-stone, but the Royal Family are expected to follow certain codes of etiquette in public which includes no selfies and not talking to one person for too long.

In the past, Kate herself has acknowledged that other members of the Firm have ‘teased’ her for her ability to get carried away with conversations, adding that it is something she has sought to correct over time.

In a 2016 documentary titled Queen at Ninety, the princess confessed: ‘I think there is a real art to walkabouts. Everyone teases me in the family that I spend far too long chatting, so I think I’ve still got to learn a little bit more and pick up a few more tips I suppose.’

When the Prince and Princess of Wales attended the wedding of Crown Prince Hussein of Jordan in June 2023, William’s subtle urge to move his wife along was showcased in a rather humorous moment.

As the royal couple reached the front of the queue to offer their congratulations to the newlyweds, Kate was seen having an animated conversation with the bride, architect Rajwa Alseif, then 29.

The conversation between the two women continued – eventually prompting William to signal to Kate with his hands that she should wrap up the conversation so that the line could keep moving.

Beginning to get a bit restless, the prince then jokingly ushered ‘chop chop’ and quietly encouraged his wife to end the conversation.

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In a quick bid to prompt his wife to move on to the next set of items, William placed a delicate hand on Kate’s back – a subtle signal that it was time to wrap up their conversation

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In the past, Kate herself has acknowledged that other members of the Firm have ‘teased’ her for her ability to get carried away with conversations. Pictured: the Prince and Princess of Wales during the formal welcome of Germany’s president

It was a lighthearted moment shared between a married couple of then 12 years and a short scene that is no doubt well-rehearsed in most relationships at some stage.

Unique to the prince and princess, the humorous interaction also showcased William’s gentle guiding role for Kate as he helped to remind her of the required royal etiquette.

At the star-studded state banquet held in honour of the German president on December 3, Kate was a vision in blue as she donned Queen Victoria’s tiara.

Royal onlookers praised the princess for her deliberate choice of jewellery – with the stunning headpiece designed by German-born Prince Albert for his beloved wife.

Featuring lotus flowers within eleven Mughal arches and up to 2,600 diamonds from Garrard in London, it was also worn frequently by the Queen Mother and only once by the late Queen Elizabeth II in 2006.

Crucially, the historic tiara also served as a key indication of Kate’s well-established role in the Firm, with Queen Victoria designating it as an ‘heirloom of the Crown’ in her death in 1901, to be ‘worn by future Queens in right of it’.

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At the star-studded state banquet held in honour of the German president that evening, Kate was a vision in blue as she donned a Jenny Packham gown while her hair was delicately crowned with Queen Victoria’s Oriental Circlet tiara

Arriving at the banquet alongside his beloved wife, a suave William was impeccably dressed in a white tie and the Windsor tailcoat.

Meanwhile, Queen Camilla wowed onlookers in a green lace evening gown designed by Fiona Clare with the girls of Great Britain and Northern Ireland tiara, alongside the Order of Germany Sash.

Inside St George’s Hall, the 45-metre dining table gleamed under the light of 158 candles and a stunning 20-foot Christmas tree which glittered with 15,000 fairy lights.

Staff declared that the event was the first time in modern royal history that a State Banquet had been held with a Christmas tree as decoration.

It was a true royal welcome – with The Duke and Duchess of Edinburgh, the Princess Royal and Vice Admiral Sir Tim Laurence, and the Duke and Duch