The Duchess of Cambridge has made her first public appearance since the birth of Prince George as she joined husband William at the start of an ultra marathon on Anglesey.

The presence of Kate at the Ring O' Fire Anglesey event was a surprise and it was only revealed on Friday that she would attend.

The Duke of Cambridge officially started the three-day, 135-mile (220km) coastal run.

Prince George did not attend the event.

Anglesey has been the couple's home since 2009 while Prince William has worked as an RAF search and rescue helicopter pilot.

The duchess joined Prince William as he met volunteers and some of the runners taking part in the Ring O' Fire event.

It is considered one of the most extreme ultra marathons in the UK and circumnavigates the island.

The route takes in a variety of terrains and ascends some 13,700ft (4,000m).

The royal couple spent just under an hour at the event greeting volunteers, runners and local residents.

The duchess was described as looking "absolutely gorgeous" by people attending.

It is thought this could be one of the couple's last public engagements on Anglesey before they leave their home there next month.

Jasmine Tomblin, six, her nine-year-old sister Holly, and their friend, Megan Emery-Jones, seven, handed the duchess a posy of flowers along with a home-made card with a picture of a butterfly for Prince George.

Holly said: "We made a butterfly for him with loads of glitter on. She said George really likes bright colours. She's pretty."

Megan's mother, Louise Emery-Jones, 38, from Menai Bridge, Anglesey, said locals would miss the royal couple.

"She's been seen shopping in Waitrose, out and about and on the beach at Rhosneigr," she said.

"They have done wonders for the tourist industry."

Earlier this month the duke gave a speech at Anglesey's annual agricultural show in one of his first public engagements since the birth of his son on 22 July.

Prince William said the island had been a "special place" during his work as a search and rescue pilot at 22 Squadron at RAF Valley.

A report into tourism on Anglesey last year highlighted the economic lift the royal couple had helped generate, as heightened coverage of the area saw an increase in the number of visitors.

In 2011 the duchess gave Trearddur Bay's new RNLI lifeboat its inaugural launch - her first official visit after her engagement to Prince William was announced - prompting huge media interest.

She also took on a volunteer role in the Scout Association, with the former Brownie hosting campfires and barbecues on the island.