21 times Kate Middleton looked her happiest ahead of 39th birthday

The Duchess of Cambridge often looks like the picture of happiness when carrying out her royal duties. Kate usually has a beaming smile on her face when meeting members of the public and when she's surrounded by her family.

Here at HELLO!, we have decided to look back at some of our favourite moments of Kate looking happier than ever as she prepares to celebrate her 39th birthday on 9 January 2021…

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Kate beamed as she and Prince William were reunited with the Queen and senior royals at Windsor Castle in December 2020, following the Cambridges' royal train tour of the UK.

The Duchess was even wearing a pair of the monarch's diamond earrings in a sweet nod to her grandmother-in-law.

WATCH: William and Kate join the Queen at Royal Ascot 2019

The royal radiated a gorgeous glow when she joined WIlliam for an engagement at the Queen Elizabeth Hospital in King's Lynn in July 2020.

The pair were seen happily speaking to staff and volunteers during the visit, which was in honour of the 72nd anniversary of the creation of the NHS.

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In 2019, Kate and Prince William made a high-profile appearance at Royal Ascot. Dressed in a stunning pale blue Elie Saab ensemble, the mum-of-three appeared to be in great spirits during the outing. Royal watchers noticed how, on several occasions, Kate was seen bursting into fits of giggles whilst mingling with fellow race-goers.

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The Duke and Duchess of Cambridge joined Prince Charles and the Duchess of Cornwall in the second carriage. Kate burst into fits of laughter as the foursome shared a joked.

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Stopping to talk to Zara Tindall, the royal beauty appeared to be in jovial spirits. The two royals seemed engrossed in conversation after they embraced each other with a hug.

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Just the day before her Royal Ascot 2019 appearance, Kate looked incredible as she joined members of the royal family for the annual Order of the Garter service, which was held at Windsor Castle.

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At one point, the Duchess was spotted chatting to Queen Maxima of the Netherlands at the Galilee Porch while waiting for the procession to begin.

In 2019, Duchess Kate turned heads at a gala, which was held in recognition of Addiction Awareness Week. The royal happily smiled at flashing photographers as she made her way inside. She chose a long white off-the-shoulder jersey midi dress by Barbara Casasola for the occasion, which suited her figure perfectly.

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Kate made another stunning appearance at Trooping the Colour in 2019. Accompanied by Prince William and their three children, it was clear for the world to see how content the Duchess looked. It was a rare opportunity for fans to see all five Cambridges out and about, as the children make rare public appearances.

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Prince Louis was, in fact, attending his very first Trooping the Colour at 14 months old. The young royal kept his mother entertained on the iconic Buckingham Palace balcony.

In April 2019, Kate teamed up with brother-in-law Prince Harry at an Anzac Day service, which was held at Westminster Abbey. They both appeared to be in great spirits as they made their way inside.

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At the Chelsea Flower Show in May 2019, Kate looked pretty as a picture in a floral Erdem maxi. Soaking up the atmosphere, the royal radiated a gorgeous glow

The Duchess of Cambridge looked relaxed in a black turtleneck, black skinny jeans and a red double-breasted blazer by Philosophy during a visit to Caernarfon, Wales in 2019.

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At one point, Kate was seen speaking to guests and she looked particularly delighted to meet a young baby.

She was also seen at the Anna Freud National Centre for Children and Families, where she opened the new Centre of Excellence at Rodney Street.

The Duchess of Cambridge made a fascinating visit to Bletchley Park in May 2019 where she met with four women, who had served with the Intelligence Corps during the Second World War.

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On 7 May 2019, the day after Prince Harry and Meghan welcomed their first child together, Kate and William looked in good spirits during their visit to London's Cutty Sark. Greeting well-wishers, Kate looked elated to be handed a bunch of flowers.

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The royal couple both shared their delight over the news of Prince Harry and Meghan's first child. Kate told reporters: "It's such a special time, obviously with Louis and Charlotte just having had their birthdays it's such a great time of year to have a baby, spring is in the air."

The royal family - including Kate - had double to celebrate as they stepped out to attend the Easter Sunday church service at St George's Chapel in Windsor in 2019, which coincided with the Queen's 93rd birthday.

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Kate also made a surprise appearance at the Queen's garden party at Buckingham Palace.

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In June 2019, Kate travelled to Cumbria for a more relaxed away day. She got into the spirit of farming as she tried her hand at sheep shearing during the visit to the Lake District.

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