The Duchess of Cambridge made a surprise stylish appearance alongside husband Prince William and brother-in-law Prince Harry at an event for young sports coaches at the London Stadium today (18 October).

Kate, 35, made her second public appearance in a week, proving that she is overcoming symptoms of her severe acute morning sickness – otherwise known as hyperemesis gravidarum. She was in high spirits for the Coach Core graduation ceremony.

The duchess was an unannounced addition to the event alongside William and Harry, and must have felt well enough this morning to decide to go along. The trio saluted 150 apprentices who have graduated from the royals' own mentoring programme and met with several familiar faces, including Judy Murray and Karren Brady.

Mother of two Kate made sure to cover up her bump on the chilly day in London, looking effortlessly stylish in a blue Balmain-inspired blazer featuring statement gold buttons by Philosphy Di Lorenzo Serafini, which retails at £760.

She paired the statement jacket with a black turtleneck jumper, black skinny jeans and ankle boots, and wore her hair in her trademark blow-dried style.

Kate is glowing during her third pregnancy, with today's engagement coming just days after she danced with Paddington Bear at an event for the Paddington 2 movie. It was also confirmed by Kensington Palace yesterday (17 October) that the Duke and Duchess of Cambridge are expecting their third Prince or Princess in April.

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Kate Middleton looked chic in a £760 blue blazer with gold buttons at the event Getty

Parents William and Kate were given two West Ham shirts for Prince George and Princess Charlotte at the football club's home in London.

The club's captain Mark Noble said: "We know that William's an Aston Villa fan so whether it gets put on or not I don't know. Whether they'll let George do that I don't know! It was a gesture from us as a welcome to the club really.

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Duke and Duchess of Cambridge and Prince Harry pose with Coach Core members as they attend the Coach Core graduation ceremony for more than 150 Coach Core apprentices Getty

"We were talking about the new stadium, football and what West Ham coming to the stadium has done for the area. It's so nice to speak to the royals. For 99% of the population they are figures from afar.

"I told my little girl, who's only eight, that I was coming to meet the royals and she was so jealous. I can't wait to show her photos. She'll think I'm more of a great dad now than I was yesterday.

"For me, getting kids doing sport instead of sitting in front of computers is great. We need to do more of this stuff to get people active," MailOnline reports.

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Duke and Duchess of Cambridge and Prince Harry were in high spirits during the event Getty

Kensington Palace made an official statement about the royals' attendance at the event, tweeting: "Congratulations to Coach Core London, Coach Core Glasgow, Coach Core Wales & Coach Core Essex for graduating today!"

Prince Harry also made a speech at the event, in which he said: "We believe that our graduates here today really are the future of coaching. They have each been on a unique journey, designed to build on their existing skills to equip them with the tools to be effective role models and mentors in their communities."