Christine Ohuruogu produced an astonishing late charge and defending champion Amantle Montsho committed racing suicide as the Briton won the world 400 metres gold medal by four thousandths of a second. Ohuruogu, the former Olympic champion, is famed for her storming home straight finishes but even she looked out of it as Botswana's Montsho entered the final 30 metres well clear. Ohuruogu, however, somehow closed the gap and timed her dip to perfection as Montsho crossed the line entirely vertical. Nobody in the stadium knew who had won but after an anxious wait it was Ohuruogu's name which came up on the board first. Montsho, looking stunned, was given the same time of 49.41 seconds but the Briton won by four thousandths of a second and broke the 29-year-old British record in the process. "I can't believe I've done that, it feels like a dream," she told reporters. "I was thinking 'do what you can, just get over the line'. The icing on the cake is the national record, that's all I wanted. Whatever you want just go for it, I am really happy I kept believing and trusting in what I could do. "It is what I have been working towards all season, it was so tight on the line and I was so desperate to win it. I just wanted my name to come up." 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." Ohuruogu, world champion in 2007 and Olympic gold medallist in 2008, had comfortably qualified for the final and started steadily as usual but was still fourth coming off the final bend. Ohuruogu then went through the field, passing bronze-winning Russian Antonina Krivoshapka (49.78) as if she were going backwards. With five metres to go it still looked an impossible task yet she somehow achieved it to underline her status as one of Britain's all-time greats. Former men's 400 metres Olympic champion Michael Johnson told the BBC: "Every 400 metre runner knows that Christine Ohuruogu is going to be dangerous on the home straight. I don't know why Montsho didn't realise that at the end."