Harper wins, Ja's Williams out of 100m hurdles final
The race was won by reigning Olympic champion American Dawn Harper in 12.56.
Running out of lane three next to Harper, Williams clocked 12.83 in a blanket for the minor places.
Second was Beate Schrott of Austria also in 12.83.
Williams has a personal best of 12.78 seconds in this event.
Speaking with reporters in London after the race, Williams expressed regret for not advancing.
"I was hoping to get into second place but I lost some time on the second hurdle. It took forever to get back on to the ground. I know I could have run a little bit better," she said.
Yesterday leading contender, National champion Brigittte Foster-Hylton crashed out in tears during the heats and Latoya Greaves did not start her race due to injury.