Christine Ohuruogu confirmed herself as arguably Britain's greatest ever female athlete by last night breaking a national record as old as she is to secure a second 400 metres World Championship crown.

When Kathy Cook ran 49.43 seconds in August 1984, few could have predicted it taking 29 years for a Briton to run quicker. Ohuruogu was just two-and-a-half months old when Cook crossed the line in Los Angeles and has spent her adult life trying to overcome that record.

Last night she did just that, producing the run of her life. Six years after winning her first world crown, the 29-year-old overcame a terrible start to surge down the home straight and pip reigning champion Amantle Montsho to the line by an incredible four thousands of a second. Not only that, her winning time of 49.41 seconds meant Ohuruogu had broken that previously elusive record.

"Today is really special because I got the national record and that's really what I've been working for all season," she said. "It has been a passion of mine and my coaches to really just strive for the British record because I kind of have everything else.

"I won in '07 and Olympic gold in '08, I have Commonwealth gold, but the national record is as old as I am. It literally is. It was set in '84 and I was born in''84. I just thank God that I was able to come away with a win today. It was a good field. The girls ran superbly well yesterday and I knew today was going to be hard.It was tough, so I'm really, really happy. It feels a bit weird now, like I'm not really here.

"Maybe in a couple of days it will settle down. It's been a whole roller coaster of emotions - it's very intense.You're just up and down the whole time. It feels a bit strange but maybe in a couple of days I'll figure out where on earth I am."

Montsho will long live to regret her failure, unforgivable for such an experienced athlete and doubly so when the most famous come-from-behind runner on the circuit was chasing her home. "I always have a bad finish. I don't know how to dip in a race," she said. "I didn't see Christine when she came. If I saw her I could maybe have put my chest out and made it."

Last night's victory was made all the sweeter by Ohuruogu's experience two years ago. Capping what was a third straight injury-plagued season, she was disqualified from the heats for a false start in Daegu - something almost unheard of in the 400m. She recovered well to take silver at London 2012 and headed to Moscow in the form of her life

It continued there and, after impressive performances en route to the final, she added another world title to the one she secured in 2007, just a matter of weeks after returning from a one-year ban for missing three out-of-competition drug tests.

"I know I'm a lot stronger," Ohuruogu said. "My body's been through war and I knew I'm brave enough to challenge."

Ohuruogu was the star of a good day for the British team, even though William Sharman was disappointed not to follow that success with a medal of his own.

Having finished the previous two world finals in fourth and joint fifth place respectively, he clocked 13.30sec to finish fifth again in a race won by the American David Oliver.

"I'm not very pleased with that, I made a mistake off hurdle one and it was hard work from there," Sharman said. "It's good to make the final but once you're in the final you have to get a medal and all I needed to do was to perform to the best of my ability. I can't wake up tomorrow morning and say I did that."

Unlike Sharman, there was to be no final berth for Asha Philip or Nigel Levine. Philip, the 2007 World Youth Championship gold medallist, could only finish seventh in her 100m semi-final. Levine exited at the same juncture in the 400m, crossing the line in 45.60s - a slower time than he managed in the heats.

The reigning world champion Dai Greene, European champion Rhys Williams and Sebastian Rodger all progressed from the 400m hurdles heats, while Katarina Johnson-Thompson closed the day sixth in the heptathlon standings.

Brett Morse crashed out of the discus at the qualification stage and James Wilkinson was unable to advance past the heats of the 3000m steeplechase.

Shelly-Ann Fraser-Pryce of Jamaica won the 100 metres, setting a world leading time of 10.71sec. She was folowed home by Murielle Ahoure of teh Ivory Coast (10.93) and the American Carmelita Jeter (10.94).