World Athletics Championships: Marilyn Okoro and Laura Muir reach 800m semi-final

Marilyn Okoro finished second in her 800m heat at the World Championships

Britain's Williams was unable to make the final of the 200m in a very competitive race dictated by Jamaican superstar Shelly-Ann Fraser-Pryce.

Hannah England goes for gold in the 1500m at 1820.

The day began well for the GB athletes with Okoro second in her 800m heat after a well-executed race, with the 28-year-old, who trains in America, registering a season's best time of one minute 59.43 seconds.

Muir finished brilliantly to secure her spot, with the Scottish athlete charging down the home straight to cross the line in a personal best time of 2:00.80.

Muir was drawn in the toughest of the heats - and was ranked seventh out of the eight runners - but she produced a stunning performance to finish third.

However world junior silver medallist Jessica Judd, who was awaiting her A Level results today, finished a disappointing fifth - with her time of 2:01.48 not enough to earn her one of the four fastest loser spots.

The 18-year-old was left in tears at the end of her race, claiming she felt she had let everyone down.

Anyika Onuora was also eliminated from the 200m heats after she slowed up in the home straight to finish fourth in 23.36.

When the evening session got under way on Thursday, Britain's former junior world champion Williams faced a tough task in the 200m semi-finals and she trailed in seventh as Fraser-Pryce cruised through ahead of Ukraine's Mariya Ryemen.

Williams said: "This has been an amazing experience. I came here wanting to compete. I feel I let myself down a bit in that race but I gave everything I had. It was so hard to race again this evening after this morning."

"These girls are some of my idols so to be on the same track as them, I can't be too disappointed. To even be here is an achievement in itself. I now feel I'm coming back into some form and hopefully next year will be a good year for me."