The Duchess of Cambridge was every bit the fashionable first-time mother in a floaty patterned top, black skinny jeans and her trademark LK Bennett wedges.
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The spotted top, by high-street label Zara, is clearly one of Kate's favourites — she wore it in the early stages of her pregnancy when she went tobogganing in Arosa, Switzerland.
With an affectionate nod to her rural surroundings, the 31-year-old completed the look with a light green tweed jacket, a chic Ralph Lauren number that she has worn on previous occasions.
Just five-and-a-half weeks after the birth of her baby boy, Kate was back to her usual svelte figure. She wore her luscious brunette locks loose and kept her make-up to a minimum, allowing her natural glow to shine through.
The new mum was full of charm and enthusiasm as she joined her husband Prince William to meet competitors and organisers at the start of the three-day marathon which sees runners circumnavigate the Welsh island.
The Duchess revealed to a well-wisher grandmother Carole Middleton had been tasked with looking after their baby son George who was safely tucked up at home asleep.
Kate was not initially expected to attend the event but nearly five weeks after the birth of her first child, the diligent royal was clearly eager to get back to work.
The Duke of Cambridge rang the bell to begin the gruelling 135-mile ultra marathon and the new parents cheered the brave runners on their way.
The tough race follows the Anglesey Coastal Path around the island which William and Kate have called home since 2009.
It is also the place where their one-month-old son Prince George has spent the last couple of weeks since travelling there with his mother from his grandparents' house in Berkshire.
Since being back on Anglesey, Kate has been getting back into the swing of relaxed island life. She was spotted stocking up on food at a supermarket in Anglesey on Monday.
Casually dressed in a striped jumper, black leggings and flat shoes, with her hair pulled back into a ponytail, the 31-year-old pushed her trolley around the aisles picking up supplies for herself, her husband and their baby boy.
Their public appearance at the race launch will be one of their last on the island before William finishes his tour of duty in September.
When he opened the Anglesey show on 15 August, William spoke of his love for the island and its residents.
"I know that I speak for Catherine when I say I have never in my life known somewhere as beautiful and as welcoming as Anglesey. The views across the Menai straits are undoubtedly among the most stunning in the British Isles.
"I know that both of us will miss it terribly when my search and rescue tour of duty comes to an end next month and we have to move elsewhere.
"From the bottom of my heart, thank you for making my wife and me so welcome when we arrived here, as you do thousands of visitors each year.
"This island had been our first home together, and it will always be an immensely special place for us both.
"Catherine and I look forward to returning again and again over the coming years with our family."