Moments that made 2008: Rebecca Adlington's second Olympic gold destroys oldest world record in book

It is a few seconds before 10.25am in Beijing on Saturday 16 August and the fingertips of Rebecca Adlington's left hand touch the wall to stop the clock after 16 lengths of the Water Cube. Simultaneously she propels herself to stardom. In winning the 800 metres freestyle final at the Olympics she becomes not only the first British woman to win two swimming gold medals – let alone in one Games – but pulverises the oldest world record in the books. And the opposition.

The photograph of that history-making touch tells its own story. Adlington, 19, is so far ahead at the end of the race that the other finalists are irrelevant. The nearest contender is Alessia Filippi of Italy in lane No 6. She is barely in the shot.

The only other moving thing on Adlington's heels for any significant part of the race is the line on the poolside monitors that denotes the previous world record. Not long after halfway, it was destined to be toast.

All of British swimming and much of Britain had expected Adlington to triumph over 800m, her preferred distance. She had, after all, already won her first gold medal a few days beforehand in her less favoured event, the 400m. She had swum the second-fastest 800m of all time in winning her 800m heat. But nobody, not even her coach, Bill Furniss, expected what happened.

"Frighteningly fast," is how he later described her 800m gold medal-winning time of 8min 14.10sec. "One of the all-time great swims," he added.

It was, it really was a performance for the ages and here is why. Adlington obliterated a record that had been set 19 years before by Janet Evans, a colossus of American swimming whose four Olympic gold medals included the 800m titles in 1988 and 1992.

Prior to the Beijing Games, Evans' world record of 8min 16.22sec, set in Tokyo on 20 August 1989, was the only swimming record still standing from the 20th century. Evans' record had also been the longest-standing women's swimming record of all time.

Adlington finished clear of Filippi by 6.13sec, the biggest margin of victory by a considerable distance at the summer's Games in any of the 34 swimming finals, male or female.

Even the gold and silver medallists in the marathon races, over 10 kilometres, were split by just a couple of seconds. For Adlington to hit Filippi & Co for more than six seconds over 800m was quite astonishing.

The teenager from Mansfield made the race her own within the first few lengths. The only stage when somebody other than her was ahead was after the first 50m, when Camelia Potec of Romania was slightly in front. By 100m, Potec had clocked 59.37sec, but so had Adlington, who then pulled clear and stayed there.

Late in the race, Potec's challenge crumbled. Filippi passed her between 650m and 700m, then Lotte Friis of Denmark, who finished in the bronze medal place, nudged her off the podium completely in the last 50m. By the time that happened, Adlington was already a double Olympic champion. She had completed the final 50m in 29.66sec, defying the laws of physics through sheer bloody-mindedness to swim faster than any of her previous lengths.

In the stands, Adlington's parents, Kay and Steve, leapt to their feet in celebration. Only an hour before, Adlington had felt so tense she had lain on the floor to quell nausea brought on because she was "more nervous than I've ever been in my life".

It transpired there was good reason. History beckoned.