DENISE Whyte's 50th birthday will probably start with anxious regrets.

A few hours later there are likely to be tears and a few recriminations.

But then grit and a determination to get through it will kick in.

Because while most people choose to celebrate their half century with a few drinks and a party, Malmesbury accountant and extreme race athlete Denise will be embarking on another challenge of a lifetime - a 350-mile pedal in the Arctic on a tandem with her husband Jon.

It is the latest in a series of adventures for Denise, known in the town by her former name, Pickering.

In 2005, already a marathon runner, she hiked and ran through intense heat and sandstorms to complete the Marathon Des Sables.

"It was a dream to do the Sahara run. I thought it would just be a one-off adventure. But I actually found I liked it."

A year later she went to the opposite extreme when she and her daughter Alison tackled the 100-mile Yukon Arctic Ultra race in less than 46 hours.

This year her companion will be husband Jon, who told her he didn't fancy sitting on the sidelines this time.

Then in May she will be lining up for the 145-mile Birmingham to London race followed later in the year by the Mont Blanc run - a mere 100 miles by comparison. Next year she is wondering about taking on a 460-miler, but hasn't yet decided whether to go by tandem.

The thought of taking part in the Sahara race first came to mother-of-three Denise back in 1999 but got put aside after her husband Jerry died.

In January last year she met Jon, who had also lost his wife Marion. They married in May.

She said: "I think we just feel that life is for living. That's why I take every day as it comes."

The tandem idea came about when they met someone at a race last year who rode with his wife on a two-seater.

Jon, a cycle engineer, went away and designed the first full suspension mountain tandem in the country so they could compete as a real team.

"I hate cycling so the tandem is the best thing for me because Jon steers it. What I have to have is complete faith in him," she said. "The only thing is that I am always second to him."

On March 17 the duo will push off from Eagle Plain in the Yukon and head across the Arctic Circle on the first 6633 Ultra race. Eight days later they should cross the finish line at Tuktoyaktuk.

It will be every bit as much a mental challenge as a physical one.

"When I get on the start line I usually think: Why the Hell am I here?' Usually I cry my way through it," explained Denise.

But the thought of her sponsors will often help her keep going. And even when she reaches the end of a race, it isn't over.

"Every time I do something I think: That will be it.' Then another event comes up and I want to do that."

The couple are paying their own expenses. But they are hoping to raise thousands for REMAP, a small national charity that provides individually designed equipment for disabled people. In fact Jon is so fired up about it he is becoming one of its volunteer designers.

Anyone who would like to sponsor the couple can do so online at www.justgiving.com/arctictandem.

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