Being the world’s best marathon runner can make you a millionaire, as Paula Radcliffe well knows. Being the world champion of the next title distance up and a rented one-bedroom flat can stretch the budget. Two hours in the company of Lizzy Hawker and you get the feeling that she likes it that way.

Perhaps not the economics of her situation, but the freedom of anonymity certainly.

Hawker is one of only two British senior world champions in athletics at present and, with Radcliffe absent after giving birth to her first child, the only one participating in the Flora London Marathon tomorrow. Yet the full glare of such a high-profile event is far removed from Hawker’s preferred environment. She is a mountain girl at heart and an oceanographer by profession.

The tenancy agreement on Hawker’s flat in Chester prevents her from hanging pictures on her walls. In the one place she is allowed to, on a door, she has suspended a photograph of the Matterhorn. “It is iconic for me, the first big mountain I climbed,” she said. “It is driving me mad not having pictures of mountains around me.”

Down at street level, Hawker is the 100 kilometres world champion — two marathons and keep going for another ten miles — having won gold in Misari, South Korea, last October. Ten days later she was on board a ship heading for the Southern Ocean as part of a British Antarctic Survey study of the ocean ecosystem’s reaction to climate change. Her luggage included a treadmill.

While road racing is important to Hawker, it is not her only horizon. The thought of aiming for the marathon at the 2012 London Olympics had not entered her head — at least not until your correspondent mentioned it — but the record time for covering the 188 miles from Everest base camp to Kathmandu is one of her dreams.

The bookcase in her living room is dominated by works on mountains. I pull out her copy of Japanese Alpine Centenary at random. “Good section on unclimbed possibilities in Tibet,” she says. Working part-time as a scientist at the British Oceanographic Data Centre, she is also training to become an international mountain leader, enabling her to take trekking tours.

But nothing animates Hawker so much as when she talks of the Tour du Mont Blanc, which she won two years ago. The husband of the woman who had expected to win the 96-mile event was not best pleased. “It was as if I did not have any right to be there because I did not live in the mountains,” Hawker, who was born and raised in Upminster, East London, and trained on the streets of Southampton, said.

Hawker had never tried anything like the Mont Blanc event and purchased her trail shoes only the week before, when a friend mentioned that specialist footwear might help. She was never a member of local club and has had a curiously unstructured climb to the summit of ultra running. “It was not like I set out as a youngster thinking I wanted to be a runner,” she said.

Hawker, 31, chuckles at how she came to be the 100km world champion, so much a journey of chance was it. Through friends she had met while mountaineering in Snowdonia, she was persuaded to enter a 40-mile track race. “It was an excuse to go away for a weekend,” Hawker said. “I had not run on a track since doing the 800 metres at school.”

Performing well enough to be noticed by the national selectors, she was soon picked to compete in South Korea. She turned it down, because it clashed with the Tour du Mont Blanc, but felt obliged to change her mind after being told that a team would not be sent if she did not go. The relative novice, who led by six minutes at one point, won by four seconds in a sprint finish.

“It had not even struck me that I would be in with a chance,” Hawker said. She is not a contender to win tomorrow but, with sub-2hr 50min her aim, she should be among the leading British women. She could challenge for an Olympic place, either in Beijing next year or in London in 2012, but becoming a specialist marathon runner is not her priority.

“My first love is the mountains but, at the same time, unless you concentrate on one thing for a while you are never going to realise your potential,” Hawker said. “Marathon, long distance, mountain running — it is hard to balance it all. Then, thrown into the equation, there is wanting to do ski mountaineering expeditions.”

Even defending her world title, next September, is in doubt. “The Tour du Mont Blanc is a week or two before, so it is one or the other,” she said. The call of the mountains is loud and, if Radcliffe is to be envied by Britain’s other world champion, it is not just for her wealth and talent. Radcliffe trains in the French Pyrenees. “That would be nice,” Hawker says. Beats Southampton.