I hope people don't need to ask but I suppose Mara has been in the shadow of Paula Radcliffe for a long time.
She has been around for a fair while, steadily improving, very consistent and after finishing second in the London Marathon she has finally shown an indication that there is much more to come.
Mara is 35 years old and lives in Japan, where she worked as a diplomat in Tokyo, but she is as British as they come.
Yamauchi ran a personal best in London to take second place
She married a Japanese guy, hence the surname, but the public here will no doubt really take to her as she is bound to see her profile soar after such an impressive performance.
Japan is a big running country and I think that moving out there has helped her. She won the marathon in Osaka last year and from there her confidence has blossomed.
In some ways she was typical of an athlete who was never going to make it on the track and instead she followed her other career.
But being a marathon runner is a 120 miles-per-week job and getting extra funding has helped her to treat it that way and make great strides.
Now she has come in second place in one of the world's five big marathons, only losing out to the current world number one Irina Mikitenko, she will be thinking, I can go faster and I can win things now.
I also think that Mara's result could be great for Paula Radcliffe
She is not old in terms of women's marathon ages either - Mikitenko is 36, Paula Radcliffe is 35, and so long as she stays healthy she will keep on getting better.
This result will be massive for Mara in two ways; one, personal confidence, and secondly her profile within the sport will increase and she will get invited to all of the major events.
I also think that Mara's result could be great for Paula Radcliffe.
To have a fellow Brit running within two or three minutes of her will spur her on when she comes back from her toe injury and provide us with some interesting competition in the build up to London 2012.
Mara delighted with personal best
In fact if you look at it we could have four world-class marathon women by London 2012 with Mara Yamauchi, Paula Radcliffe, Jo Pavey and Liz Yelling.
Mara put in a genuinely good run in London, her benchmark has now shifted, the question will now be, can she push on and fully come out from behind the shadow of Paula? One thing is for sure, it is great news for British running.
I thought the men's race was an interesting one. Unfortunately I think the pacemakers went too fast to start with and fell off the front too soon, otherwise we might have seen the world record tumble.
We saw a course record, we saw a personal best but Sammy Wanjiru is only 22, he is still learning and he has got no fear.
The way he put in surging runs towards the end, every time Tsegay Kebe pushed him, is not something we usually see in marathon running.
But with the pair of them being the same age there will be exciting battles ahead from those two. It was a bit of a shame Martin Lel had to pull out because that would have added even more to the mix.
And for London, well it was a beautiful day, with the top runners in the world running at their best which showed that London is right up there as the number one marathon, and no-one can argue with that.
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