AS A professional athlete all her adult life, Paula Radcliffe has never had a job in the everyday working world. How marked the contrast with Mara Yamauchi, who, in Radcliffe’s absence, is likely to be Britain’s highest finisher in the Flora London Marathon on Sunday. A diplomat in Japan for the Foreign and Commonwealth Office, Yamauchi was lost to international sport for six years.

Now 32, Yamauchi, who has put her diplomatic career on hold, has been improving consistently since being selected to run in a relay for Britain in 2004. Before that, her last international outing was in the 1998 World Universities Cross Country Championships, in which she finished sixth. She has improved in each of her four marathons and expects another advance on Sunday.

“I want to break 2hr 26min at least,” Yamauchi said. Buoyed by her unexpected bronze medal over 10,000 metres in the Commonwealth Games in Melbourne, the former Mara Myers, now married to a Japanese, has set her sights on becoming the second-fastest Briton in history behind Radcliffe, the world record-holder, who is forced to miss the race because of injury.

It may be a far cry from advising the Japanese on English football hooliganism, as she did at the time of the 2002 World Cup finals, or diplomatic engagements that have brought her into contact with Baroness Thatcher and Jack Straw, but professional satisfaction on Sunday will be to send Veronique Marot down to No 3 on the British all-time list.

Marot set a British record of 2:25:56 in London in 1989, a mark surpassed now six times by Radcliffe but unmatched by any other Briton, including Liz McColgan, a former winner of the London and New York marathons. After recording 2:39:16 for seventeenth place in the 2004 London Marathon, soon after resuming serious training, Yamauchi finished tenth last April in 2:31:52.

Selected by Britain for the World Championships in Helsinki last August, Yamauchi improved by another 26sec for eighteenth place, despite the twisting course and warm weather. In her most recent marathon, she recorded 2:27:38 for fifth in Tokyo in November.

Yamauchi’s early interest in running was developed through Oxford University and, after graduating and joining the FCO in 1996, she found it difficult to fit training around her work. In 1997, though, with her medium-term future earmarked for Japan, she was put on a two-year language course. During the first year, in London, she rediscovered the time for training.

“I had lessons in the morning and homework in the afternoon, so I had more time,” Yamauchi said. She qualified to represent Britain at the 1997 European Cross Country Championships, but soon the running had to be put to one side again. “The second year of the language training was in Japan and, for the next four years in Japan, I did not have time to run seriously and work,” she said.

“I kept up steady running and, when it came to the end of my posting in 2002, I was 29 and due to go back to the Foreign Office in London. I wanted to give running a serious go again, so I chose to go part-time from January 2003. When I left for Japan I was on an upward curve. I did not have any regrets about going, but I felt there was unfinished business on the running front.”

Since January this year, and up until the 2008 Beijing Olympics, Yamauchi has taken unpaid leave and is living in Ota-ku, a suburb of Tokyo, with her husband, Shige. “My husband has a job here and the Foreign Office has a scheme where people accompanying their spouse overseas can take unpaid leave and return in the future,” Yamauchi said. “But I am still employed by the FCO.”

It was while Baroness Thatcher was visiting Japan that Yamauchi met the former Prime Minister. “She attended a dinner at the Embassy and I was asked to interpret because the person she was sitting next to did not speak English,” Yamauchi said. And Jack Straw? “He was visiting after the World Cup and we showed him the publicity we had done for the England team,” she said.

“The Japanese had this image — English football equals hooliganism — and one aspect of our work was trying to persuade them that not all English football fans are hooligans.” Other diplomatic work that Yamauchi was engaged in included advising Hungary and Slovakia on their attempts to join the EU and Nato, as well as following Japanese politics and sending reports back to London.

From Yamauchi’s flat in Tokyo, she paints the scene. “We are facing a river,” she said. “You cannot see it, because there is a flood barrier, but you can see the cherry trees and, in the far distance, Mount Fuji.” It was not, sad to say for the sake of this tale, far-sighted parents who named their daughter Mara, as in Mara the Marathon.

“It’s an odd coincidence, being the first half of marathon,” Yamauchi said. “But my parents lived in Kenya for many years and I was named after a river there.” So she is a little bit Japanese, a little bit Kenyan. And perhaps, on Sunday, she can be a little bit Radcliffe, too.