He knew he was guaranteed a gold medal, so when Aled Davies launched his final discus throw, he could barely wait for it to land before taking off on a lap of honour that brought the Olympic Stadium to its feet.

Davies, already a bronze medal winner in the shot put, wheeled away in delight after breaking the European record with his last throw, then draped himself in a Union flag and declared himself “the happiest man on the planet”.

His gold medal in the F42 final meant Great Britain’s track and field athletes had surpassed the medal tally they achieved in Beijing after just two and a half days of competition.

Davies, 21, wears a brace on his right leg after he was born with a condition which means that it does not function properly.

He could barely control his emotion as he turned to the crowd and held his hands aloft in delight.

He had the added bonus of becoming the first athlete to receive a gold medal from the Duchess of Cambridge.

The Duchess had been invited to present two medals and her spokesman said it was a “happy coincidence” that the first recipient was British.

With a week of competition to go Britain is almost halfway towards its target of beating its Beijing tally of 102 medals.

Davies led the charge on another gripping day of athletics for ParalympicsGB, with Stefanie Reid, whose leg was amputated, taking silver in the long jump; Graeme Ballard, 32, who has cerebral palsy and epilepsy, winning silver in the T36 100m final and Libby Clegg, 22, who is partially sighted, taking silver in the T12 100m.

Clegg was cheered on by her brother James, 18. Hours earlier James, who has the same condition, won bronze in the S12 100m butterfly.

Ballard had considered quitting athletics after the Beijing Games, when his funding was cut.

After his win Davies said: “I am probably the happiest guy on the planet right now. It was a tough competition. But I dug deep. Four years of hard work for this – it’s nice to give something back to ­everyone.

“I’m just so happy I performed. I’ve worked so hard so to deliver, and to give something back on the biggest stage, I can’t believe it.

“This crowd is incredible. Everything here is phenomenal. It’s sad to know that was my last event. This place is addictive. I’ve got a lot of love for this crowd.”

He added: “Everyone was in tears at the end – it made me cry. They’ve had to put up with all my mood swings so it’s great to give something back.

“Sometimes I’m calm, sometimes I get aggressive. I was going head-to-head with the Iranian guy [Mehrdad Karam Zadeh] who I’ve been in competition with for some time.

“He threw well in the first round and I thought ‘I can do better than that’. And then I threw better.”

The Welshman’s road to glory began when he was 13. As he watched the Paralympics on television, he realised that some of the athletes had the same disability as him.

The sports management student from Bridgend had started as a swimmer, competing in able-bodied events for his local club. He had not even considered competing in events for the disabled.

“Disabled was seen as different back then and I really didn’t want to be associated with that,” he said before the Games. “I always saw myself as able-bodied.

“I saw a bit of the Paralympic coverage in 2004 and I thought, ‘Oh yeah, that guy’s got the same as I’ve got.’ I thought then I would love to be in the Games. I remember telling people ‘I’ll be on the podium one day’. And here we are.”

Earlier in the day, Reid, 27, set a lifetime best as she leapt to a silver medal in the long jump.

Reid, who lost her right leg below the knee in a boating accident aged 16, launched herself to 5.28 metres only to be denied gold by a whisker.

“If someone had told me four years ago that the best to come was a silver medal it would all have been worth it,” she said. “It has just confirmed to me that I love what I do.”

She was going for a second medal last night in the 200m and will run in the 100m later in the week.

After the accident her parents had been called to her hospital room to say their goodbyes because the boat’s propeller had caused so much damage.

She had been in despair after being told that her foot had been amputated, but a no-nonsense nurse reignited her lust for life. Recognising her competitive spirit, she told Reid that a younger girl in another ward had lost both legs and was sitting up smiling.

The girl did not exist, but the nurse’s white lie did the trick and spurred Reid to recovery.

“I was in hospital in Toronto having lost my leg and I didn’t know if I wanted to continue,” she said. “The nurse was the first person who expected something better of me. She shocked me but she read me right. She helped me realise I could still be competitive, I just had to channel it in different ways.”

Reid said that the accident had made her realise at a young age what mattered in life. “I’m so grateful for a second chance,” she said.

The biochemist represented Canada in Beijing, clinching bronze in the 200m, before switching allegiance to Britain, the home country of her parents.