It was the first world record in a major championship by a British track athlete since David Hemery won the equivalent event in the Mexico Olympics 25 years ago.
Gunnell's coach of long standing, Bruce Longden, had said before these championships that if it required a world record to win the title, Gunnell would run it. The challenge of Sandra Farmer-Patrick, far stronger and more prolonged than it had been when she took the silver in Barcelona last summer, obliged Gunnell to live up to that prediction.
In the 40 metres between the last of the 10 hurdles and the finish, the 27- year-old farmer's daughter from Chigwell won a race-within-a-race - untechnical, brutally simple - that searched her character to the furthest limits. For the first time in a season of six consecutive victories, Gunnell found herself running to the line in second place. Calling on all the speed she has shown over shorter distances this year, she moved inexorably up to and past her agonised opponent.
After crossing the line less than a metre behind, Farmer-Patrick fell splay-legged on to her face in exhaustion. She had run 52.79, also inside the seven-year-old world record of 52.94 set by Marina Stepanova of Russia. As the American lay prone, Gunnell walked on as if in a daze.
'I didn't start celebrating in case I made a fool of myself,' she said. 'I wasn't sure I had won it.' The performances of the bronze medalist, Margarita Ponomaryova of Russia, and the fourth-placed Kim Batten of the US, who ran respective personal bests of 53.48 and 53.84, underlined the race's claim to being the finest in the history of women's 400m hurdling.
'World champion, Olympic champion and world record-holder,' Gunnell said. 'It's a dream come true. I knew it would be fast, but I wanted to win it most. After the last hurdle, I had to keep on digging deeper and deeper. Sandra ran a fantastic race - I couldn't have done it without her. I kept saying to myself, 'you can run faster than anyone else in this field'. But the world record is a total bonus.'
She achieved it despite having suffered with a cold and sore throat within the last week. 'There is definitely more to come,' she added.
The night before, she had dined with Colin Jackson and the man who had already added world to Olympic gold in the 100m, Linford Christie. 'They got me in the right frame of mind,' she said. 'They told me, 'You are the best out there. You are the best prepared. Don't lose it'. On the coach coming up here, Linford and I were sitting down going through all the build-up of the race. He said: 'Do you want me to go through the airport first when we get home and leave you at the back?' That really spurred me on.'
Merlene Ottey of Jamaica, who earned prolonged and sympathetic applause at the 100m medal ceremony after being given the silver behind Gail Devers in a race many saw as being a dead heat at least, earned the only possible consolation prize with a gold medal in the 200m.
In the final stages, as if distracted by the thought of what she was about to achieve after more than 10 years of silver and bronze medals, she lost her rhythm perilously and almost stumbled across the line. 'I wanted to win so much that I ran the first 100 metres too fast and I was having problems over the final 10 metres.'
Unlike on Monday night, when she was eventually judged to have lost by 0.001sec, she had done enough, recording 21.98 to the 22.00 of the faster- finishing Olympic champion, Gwen Torrence of the United States.
The men's 400m hurdles final also saw victory for an Olympic champion as Kevin Young held his lead down the straight to cross the line first in 47.18, ahead of a line of three straining rivals, Samuel Matete of Zambia, Winthrop Graham of Jamaica and Stephane Diagana of France, who finished in that order.
Young, who won 26 consecutive races from the start of 1992 until Matete beat him last month at Crystal Palace, had been under pressure after suffering further defeats by the Zambian and Graham.
Sergei Bubka, who failed to record a height in the Olympic pole vault final, restored his championship credibility by winning a fourth world title with 6.00 metres.
Having done his bit for the Gunnell cause, Jackson offered proof of his statements of the day before that he was fit again after problems with his foot and back by qualifying for tonight's 110m hurdles final in 13.13.
Jack Pierce of the United States was the quickest man into the final in 13.11. 'If Pierce goes under 13 seconds in the final he has got a chance,' Jackson said. 'But I'm going to go under 13 seconds no matter what happens.'
His team-mate, Tony Jarrett, overhauled Tony Dees of the United States to win his semi-final in 13.14, his fastest time of the season and only 0.01 outside his personal best.
John Regis, Britain's only representative in the 200 metres, also reached his final today, running third in the fastest semi-final won by Mike Marsh in 20.10; Steve Cram and Matthew Yates successfully negotiated the opening round of the 1500m.
Results, Sporting Digest, page 31