- London 2012 - Swimming
Bronze again for Adlington after stunning Ledecky swim
Adlington, the defending champion in the longer event from four years ago, was expected to win again - with perhaps Denmark's Lotte Friis providing a strong challenge. But Ledecky stunned both stars with an outstanding swim - staying on world record pace for much of the race before ultimately touching the wall in 8:14.63 seconds.
With Spain's Mireia Belmonte Garcia also finishing strongly to snatch silver, Adlington was forced to settle for bronze - just as she did in the 400m - as Friis ultimately finished fifth.
Adlington finished just over five seconds behind the victor, although she insisted she was happy with bronze.
"That was an incredible swim from her [Ledecky]," Adlington said. "I think she is only young, 15 or something.
"I would have liked that time to be a bit quicker, I don't know what happened. I gave it my absolute all - I'm sorry I couldn't get the gold for everyone but I'm still delighted to get bronze."
Ledecky, who revealed she had sliced about 20 seconds off her best time in the event over the last year, was amazed at her ability to keep calm and deliver on the biggest stage of her career to date.
"I just wanted to go out controlled, and then get at it. I've really learned how to train hard and train fast and it's really paid off. It's incredible," Ledecky, the USA's youngest competitor at these Games, said.
"I had to calm myself, but I was a lot less nervous for this race than my prelims."
The 23-year-old was bidding to become the first British woman ever to win three Olympic gold medals, but nevertheless became the first British woman to win four medals of any colour.
She added: "It's one of those things that the 800m was my event. The pressure and everything, the expectation has been a battle going into this meeting."
Prior to Adlington's race, Michael Phelps defended his 100m butterfly crown with a remarkable comeback at the Aquatic Centre.
Having lost to South Africa's Chad le Clos in the longer version of the event earlier in the week - and only narrowly defeating Milorad Cavic four years ago - Phelps looked in trouble as he turned for home outside the medals, but the greatest Olympian of all time stormed home to grab a clear victory to go with his 21st Olympic medal.
Le Clos shared second with Russia's Evgeny Korotyshkin, with Cavic just outside the medals.
Phelps was great but he did not set a world record - unlike 17-year-old phenom Missy Franklin, who decimated the field to claim a remarkable victory in the final of the 200m backstroke.
Britain's Lizzie Simmonds, meanwhile, was a valiant fourth - having been on Franklin's tail for much of the race she just faded as the field came down the final length.