THE alchemist in Jessica Ennis turned Sheffield steel into gold last night, winning Britain's first athletics medal of the 2012 Olympics in the women's heptathlon.

Ennis was so far in front that the final event, the 800m was almost a formality. But she kept her grip. Boxed in with 110m to go, she darted through a gap and scorched home in 2:08.65, raising her arms as she crossed the line.

There were tears of joy before she completed a lap of honour wrapped in the union flag. The crucible of the London stadium proved too hot for a formidable line-up of rivals as Ennis smashed her own British heptathlon record, with a total of 6955.

She won by 327 points, setting three life-time bests and reclaiming the crown won for Britain by Denise Lewis in Sydney 12 years ago.

Tatyana Chernova, the Russian who denied Ennis world gold last year in Daegu, finished second (6628), with Ukraine's Lyudmila Yosypenko third (6618).

The triumph moves Ennis, 26, to fourth on the all-time list, closing in on the European record of 7032 set by Sweden's Carolina Kluft. The world and Olympic record of 7291 was set in Seoul by Jackie Joyner-Kersee.

Ennis' high jump best of 1.95m would have been worth a further 127 points. She cleared 1.86m, modest by her standards. Producing all one's best performances in one contest is a big ask, but even the world record is now not beyond her. A time of 2:05.69 last night would have taken her through the 7000-point barrier.

Ukraine's reigning Olympic champion Nataliya Dobrynska flopped with a dismal 3.70m in the long jump, and then withdrew.

The defending silver medallist Hyleas Fountain dried up having been fifth, just three points short of bronze, at the start of the day

The American had a poor long jump and then managed only 21.60m, last in the javelin, and abandoned.

These two events were previously Ennis's Achilles heel. A poor javelin last year cost her the world title. Yesterday she laid her demons. She was just three centimetres short of her long jump best, with 6.48m, and her javelin (47.11m) was one of three lifetime bests.

On the opening day of the event, Ennis won the hurdles in a British record of 12.54 which would have won every Olympic hurdles title bar two since 1972, and her 200 in 22.83 was her best ever.

She will rest before deciding whether to contest the 100m hurdles tomorrow.

Sandra Perkovic of Croatia took women's discus gold with 69.11, while Chinese student Chen Ding, 21 tomorrow, set an Olympic record to win the 20k walk with 1:18.46.

Martyn Rooney (45.36) was fastest of the three Brits who advanced to the 400m semi-finals in his bid to become the first Briton to win since Scotland's Eric Liddell, in 1924.

Rooney was 11th fastest but Nigel Levine and Conrad Williams will do well to go further.

The hopes of the defending champion and world No.1, the USA's LaShawn Merritt, fell flat, unhinged by a hamstring injury.

Merritt, who served a doping suspension for a drug contained in a penis enhancement cream, walked off after 200m. "This was my life's race," he said. "I have been having treatment since I got here.

"When you want it so bad, you do what it takes, but I did not want it to end my career."

Three women went under 50 seconds to reach tomorrow's women's 400m final, with Christine Ohuruogu second in her heat (50.22) seventh fastest. Lee McConnell (52.24) was seventh in the fastest heat but was 0.34 quicker than Shana Cox, which will do her relay hopes no harm.

GB athletics captain Dai Greene had to endure watching two further semi-finals to see if he would qualify for tomorrow's 400m hurdles final after placing fourth.

"That's no way to perform if you're world champion," he said. "I was going down the home straight and couldn't catch them," Greene said before learning he had done enough to qualify as a fastest loser.

"I don't know what happened, I wasn't there. I'm devastated. I'm shocked and feel like I've let everyone down."

While the Welshman survived, he saw his training partner Jack Green clatter the third flight and crash to the ground before pounding the barrier on the ground, and walking off in fury.

"That isn't conducive to running quick times in the 400 hurdles," Green said. "It's a lack of experience in the event. I felt a headwind going into my face ahead of hurdle three, so I felt: 'I've got to pick this up'.

"Then I just messed it up. I'm absolutely gutted. It was a stupid fall and a complete waste of time. I've had problems with my hip in the past but I'm far too angry for anything to hurt at the moment."

Holly Bleasdale qualified automatically for tomorrow evening's pole vault final, clearing 4.55m. "If the crowd get behind me and lift me up, then I can be even better," she said. "They were amazing today and I'm so excited."