Laura Muir fought back the tears as her medal dream was missed by fractions at the World Championships in London.

1500m hopeful Muir arrived in the capital as arguably British Athletics' best medal hope outside Mo Farah, with her name already being mentioned in the same breath as double Olympic champion Kelly Holmes.

But after finishing fourth in a dramatic finish with South Africa's Caster Semenya, the Scot looked shell-shocked.

"It's fourth, what can I say, I'm just gutted," she said.

"I gave it everything I could but in that last 50 metres I just tired up at exactly the wrong moment and I wasn't strong enough.

"It's just so close to getting that medal but I couldn't physically react in those final metres, there was nothing left.

"I knew I had to take the race out and then ease off and not use up too much energy. I executed my race plan exactly as I planed and ran as hard as I could, the others were just better.

"I'm making the right progress, every year is a huge step for me. I've had some setbacks this year and there is a lot more than I can do."

Semenya was controversially forced to undergo gender testing by the IAAF before being cleared to compete in 2010 due to a rare condition.

Semenya – who won Olympic gold over 800m in 2012 after Russia’s Mariya Savinova was found guilt of a doping infringement – has levels of testosterone three times higher than is expected in women due to hyperandrogenism.

And Muir - who has refused to talk about her rival throughout the championship build-up - again dodged questions last night.

There is no doubt about Muir's talent and it should only be a matter of time before she delivers on the big stage.

Sixth the last worlds, fifth here, the trajectory is right but tactically she may look back on this race as a gilt-edged opportunity missed.

Kenya's Faith Kipyegon, last year's Olympic champion, kept her cool to kick clear for gold with American Jennifer Simpson taking silver and Semenya pipping a fading Muir on the line.

Muir took the pace out fast - just as she did at last year's Olympics - but the second lap slowed dramatically before the speed was injected again.

Semenya produced a blistering 57.8 second final lap coming from ten metres back at 150 metres to snatch a medal

It was an utterly breathless race, bewildering tactically and totally compelling but Muir was backed to rebound by team-mate, captain and fellow Scot Eilidh Doyle.

"The whole team admires Laura because she is so gutsy," she said.

"When you see her around she is so quiet and timid but on the track she is a warrior and she's my absolute favourite runner. We know she always competes and runs her heart out and he's got an amazing future in the sport."

Muir will be back in action in the 5,000m but is playing down her medal chances.

"I'm still planning for that 5,000m, I just need to talk with my coach," she added.

"I'm pretty inexperienced over the distance, I've only run it once this season, so we'll just have to see."

You can help the next generation of young British athletes by getting involved in SportsAid Week this September with London 2012 hero Greg Rutherford MBE. Find out more about how you can support the week of fun and fundraising by visitingwww.sportsaid.org.uk/sportsaidweek