Kelly Holmes ran another perfect race to take a wonderful 1500m gold and make Olympic history in Athens.
Holmes, who won 800m gold on Monday, set a new British record with 3 minutes 57.90 seconds when it mattered most.
She becomes the first Briton for 84 years to achieve the Olympic middle-distance double.
Holmes sprinted down the home straight to finish three metres clear of Russia's Tatyana Tomashova, with Romania's Maria Cioncin in bronze.
"I can't believe it - I'm gobsmacked," Holmes said afterwards.
"After the 800m I had a lot of confidence and I was feeling good going through the rounds, but these girls are really good and I had to focus more than ever in that race.
"I was trying to place myself in the right position and put myself where I had to make a move.
"I wouldn't ordinarily move up as quickly as I did, but the pace was so quick.
HOW KELLY HOLMES COMPLETED THE DOUBLE IN ATHENS
Start of the 1500m
Looks composed as she
waits for the gun
Three laps to go
Stays safe at the back with Russia's
Natalya Yevdokimova setting rapid pace
Two laps to go
Begins to move through the field, keeping an eye on leading Russians
One lap to go
Gets a shove from Polish runner Lidia Chojecka as she moves into contention
200m to go
Accelerates smoothly round top bend and into fourth
100m to go
Goes wide and powers past leaders
Sprints clear and hangs on to take glorious second gold
"I had to use all my guts to hold on for dear life - I was running as fast as I could."
There was huge British support in the stadium when the final got under way and
as in the heats, Holmes, who was 100-1 to do the double before the Olympics began, continued her tactic of racing at the back of the pack.
She was eighth out of the 12 at the bell but moved up to third at the 150m
mark and was so much in control coming off the top bend that she had the time to look around her to check on the position of her rivals.
In contrast to her 800m triumph, she could afford to smile and raise her arms in triumph as she crossed the line, almost unable to believe the magnitude of what she had achieved.
British running greats Steve Ovett, Sebastian Coe and Steve Cram all failed to win the 800m and 1500m double during their careers.
Indeed, the only other Briton to manage the feat was Albert Hill in Antwerp in 1920.
Holmes is only the third woman from any nation in Olympic history to do the double, after Tatyana Kazankina of the Soviet Union in 1976 and Svetlana Masterkova of
Russia in 1996.
Her achievements in Athens have also seen her become only the seventh British woman to ever win a track and field Olympic gold.
The 34-year-old follows in the footsteps of Denise Lewis (Heptathlon, Sydney 2000), Sally Gunnell (400m hurdles, Barcelona 1992), Tessa Sanderson (Javelin, Los Angeles 1984); Mary Peters (Pentathlon, Munich 1972),
Ann Packer (800m, Tokyo 1964) and Mary Rand (Long jump, Tokyo 1964).
Holmes' mother, Pam Thomson, watched the nail-biting race with family and friends.
She said: "Words simply are not enough at a time like this.
"Kelly has had a lot of downs in her career and has always thought that
something will go wrong when she's at the top.
"But Saturday was her night and she was just amazing."
Reflecting on Holmes' success, Lord Coe told BBC Sport: "Kelly has joined a very select band of athletes.
"A lot have tried to do the double, but few have actually done it.
"To run the way she has, with such purpose, is truly phenomenal."
Sports Minister Richard Caborn added: "She is such an inspiration to thousands of young athletes back home."
Holmes' triumph came on another superb night for GB athletics.
British fans inside the Olympic stadium had barely finished celebrating the 1500m, when the men's 4x100m relay team claimed a shock gold, relegating the much-fancied Americans to second place.
The results mean that Team GB has now beaten its medal tally from Sydney four years ago.