All eyes on Pippa Middleton again as she slogs across the Highlands in charity event

The Duchess of Cambridge's younger sister took part in the sporting challenge as part of a team raising money for charity. She was one of more than 700 competitors who ran and cycled 50 miles coast to coast, from Kintail in Wester Ross through Glen Affric to the finish line in Beauly.

Middleton arrived in style, stepping out of a helicopter just in time to register for the event. Looking toned and tanned, she smiled at well-wishers but declined to talk to photographers vying to capture an image of her famous rear.

After collecting her yellow and orange wrist bands, Middleton performed a series of warm-up stretches before joining the queue outside a sheep shed, which housed a portable toilet. At 11am, she lined up with team mates Jake French and Rose Laing for the first leg of the annual challenge, dubbed by veterans "50 miles of midsummer madness".

To the delight of organisers, the rain that was forecast held off and the event got underway in warm sunshine. The first leg involved a gruelling 20 mile run, followed by a hilly 30 mile bike ride through some of the country's most spectacular scenery. Entrants can treat it like a race or take a more leisurely approach. The fastest time in the event's 28-year history is 3 hours, 13 minutes and 31 seconds and the slowest ten hours, 25 minutes, by a competitor who was hampered by two punctures.

Yesterday was Middleton's first Highland Cross, but her team, the Affric Sprats, took part last year, raising more than 3,000. Middleton was among the contributors in 2010, pledging 40 to the team, and volunteered to join in this year. She is believed to have been in training since before the Royal wedding, where her appearance in a figure-hugging bridesmaid's dress won her legions of fans around the world.

So far the Affric Sprats have raised 4,122 - a little short of their 5,000 target - but the sum could be topped up by personal sponsorship.

On the team's Just Giving page there was no evidence of donations from Middleton's sister, Kate, or her husband, Prince William, but they may have chosen to make anonymous contributions. Along with details of the event, the team wrote: "As June fast approaches its time for the Affric Sprats, aka Jake French, Rose Laing and Pippa Middleton to participate in yet another epic Highland Cross Challenge.

"The Highland Cross is a 50 mile duathlon traversing the Highlands coast to coast!

"It supports the most wonderful small Highland charities which are often forgotten. Amongst them Lochaber Action on Disability and Children's Hospice Association Scotland. These charities are chosen carefully and they benefit hugely from the support they get from the Highland Cross year after year. As this is only a small event every single penny goes a long way. Please please muster together a generous donation, giving whatever you feel you can, how ever small, and help us raise another fantastic amount to this worthwhile cause. All support most welcome at the finish line in Beauly. With much love and thanks, Rose, Jake and Pippa."

Last night Middleton arrived in Beauly, tired and muddy but smiling broadly after completing the course in five hours and nine minutes. "I am really tired," she said. "It was one of the toughest things I have done. I don't know if I will do it again but I am really pleased to have finished."

John Fraser, the event organiser, said: "That is a cracking result for her. She will probably finish in the top 20 women, and maybe in the top 15. Plus she will also be well inside the top 200 of men finishers. She was complaining that the wind was against her most of the way, as were most of the competitors, and she could have finished a lot quicker. Pippa is obviously a very good athlete."

The inaugural Highland Cross event took place in 1983, when a challenge was issued by the Inverness branch of the Fire Services National Benevolent Fund to ten civil emergency services and military units in the Highlands. They were invited to provide teams of three to make their way on foot and on bike across the Highlands from Loch Duich to Inverness, a distance of about 60 miles. Each team had to be sponsored for a minimum of 100, with the money going towards the newly launched Highland Scanner Appeal. This year's Cross featured 240 teams and the money raised will go to a number of nominated charities.

Full results of yesterday's event will be available today on the Highland Cross website at www.highlandcross.co.uk