Britain's Mo Farah claimed his second gold of the 2012 Olympics with a stunning win in the 5,000m.
The 29-year-old had already won the 10,000m earlier in the Games.
Farah, whose wife will give birth to twin girls very soon, told BBC Sport: "Those two medals are for my two girls. They can have one each."
Britain claimed their 28th gold of London 2012 when boxer Luke Campbell won his bantamweight final, beating Ireland's John Joe Nevin.
Campbell floored Nevin in the final round of their three-round contest as he recorded a 14-11 victory at ExCeL.
It was GB's second boxing gold of these Games following Thursday's success for Nicola Adams.
"I'm lost for words, very emotional," said Campbell. "It's something I've worked for all my life. I can't believe it. I'm very proud to be from Hull and I really appreciate all the support both there and here in London."
Diver Tom Daley came close to adding another gold for Britain but had to settle for bronze in the final of the 10m platform at the Aquatics Centre.
American David Boudia took the title, with China's Qiu Bo taking silver.
"I gave it my best shot, I gave it absolutely everything," said Daley. "I'm just so happy. I can't wait to see my family and have a massive bundle!"
Farah hit the front with 700m left and was never headed, covering the last lap in under 53 seconds to hold off Ethiopia's Dejen Gebremeskel to win in 13 minutes and 41.66 seconds. Kenyan Thomas Longosiwa was third.
"It's unbelievable," Farah added. "I was feeling tired coming into the race. When I took the lead, I knew I had to hold onto it. It has all worked out well. Two gold medals. Who would have thought that?"
Prime Minister David Cameron tweeted his admiration for the double gold medallist shortly after the race.
"@Mo_Farah is an Olympic legend and a true British hero," he wrote. "We can all be proud of his extraordinary achievement."
London 2012 chairman Lord Coe, a two-time Olympic 1500m champion, added: "Mo Farah - a distance running great and arguably the best British runner of all time."
Farah joins an elite band of runners to win both the 5,000m and 10,000m at a single Games. He emulates the feat of Kenenisa Bekele (2008), Miruts Yifter (1980), Lasse Viren (1972 and 1976), Vladimir Kuts (1956), Emil Zatopek (1952) and Hannes Kolehmainen (1912).
Britain now have 62 medals - 15 more than they won at the 2008 Games in Beijing - and have cemented third place in the London 2012 rankings behind the United States and China.
Team GB could add two more golds on Sunday - the 16th and final day of action - when boxers Anthony Joshua and Fred Evans fight in their respective finals.
Usain Bolt won his third gold of the Games - and the sixth of his career - by helping Jamaica win the 4x100m relay final in a world record time.
Bolt, who defended his 100m and 200m titles earlier in the Games, ran the final leg as the Jamaicans finished ahead of the United States in a time of 36.84 seconds, the first time anyone has run sub-37 secs.
"It is always a beautiful thing to end on this note," said the 25-year-old sprinter. "It is a wonderful feeling. It was a great Olympics and I am happy. I wish we could have gone faster, but I guess we leave room for improvement."
Ed McKeever got the penultimate day of these Games off to the perfect start for Britain by powering to victory in his kayak event at Eton Dorney.
"I'm so happy," said the Englishman, who is nicknamed the 'Usain Bolt of the water'. He added: "It sounds stupid but it's not elation, more relief, and I'm so happy to do it front of a home crowd."
Liam Heath and Jon Schofield also won a kayak medal for Britain, teaming up to win bronze in the K2 200m final.
"With a headwind like that, especially when you're going at that speed, it's really tough but I'm so pleased," said Heath.
Hopes of another bronze for the host nation were dashed when the men's hockey team were beaten 3-1 by Australia.