Black, who turned 30 in March, secured his place in Atlanta by winning in 44.39sec, taking 0.08sec off the time David Grindley set at the 1992 Olympics. In his wake, unprecedentedly, he dragged three other British runners under 45 seconds.
Du'Aine Ladejo, who beat Black to the European title two years ago, defied general expectation by taking the second automatic qualifying place in a personal best of 44.66sec, with Iwan Thomas taking third place in 44.69, 0.03sec ahead of fellow Welshman Jamie Baulch.
Ladejo and Black then engaged in a press conference exchange more reminiscent of a boxing occasion which ended with Ladejo betting pounds 1,000 that he would beat Black's record this season.
Black, whose career has reached new heights after repeated problems with illness and injury, expressed delight at regaining the record he first gained in winning the 1986 European Championships in 44.59sec. "I have been missing this record," Black said. "I have been Britain's No1 400m runner throughout the last 10 years. Sometimes other people have come along, sometimes they haven't."
Ladejo responded: "I am sorry to say this, Roger, but you won't be holding that record for long."
Black, barely maintaining his exasperation - "Oh no, Du'Aine. You are so predictable" - then responded with a challenge: "How much money do you want that you will run 44.39 this year? Put your money where your mouth is."
To which Ladejo responded, "Okay. I'll put a grand on it."
It was the second fastest 400m time of the year for Black, who, despite equalling his previous best last year, gambled on having a cartilage operation before Christmas which has left him running pain-free for the last five months. "This business is not difficult when you are healthy," he said. The business on the track, at any rate.
Whatever happens, the prospects for Britain's relay team in Atlanta appear, if not golden, then bright silver.
Black's training partner Jon Ridgeon also had a memorable day, winning the 400m hurdles in 49.16sec to confirm his comeback from injury after four Achilles tendon operations.
Ridgeon had pulled out earlier in the week after having an operation for haemorrhoids, but decided to run after managing to clear two hurdles in practice on Thursday.
In the women's 400m hurdles, Sally Gunnell took another step back towards her form of old with victory in 54.65sec, her best of the season. "I needed that," she said. "The stride pattern is beginning to come together for me now."
Kelly Holmes, winner of Saturday's 800m in a world best this year of 1min 57.84sec, added the 1,500m title as she finished 30 metres clear in 4min 08.14sec.
She thus became the first woman to complete this double at the AAA Championships since Diane Leather won the 800m and mile in 1957.
Holmes may yet double up in Atlanta, but she is more likely to decide on the event which will give her best medal potential after further races this month, ending with Gateshead on 30 June. "At the moment I'm favouring the 800m," she said. "But we'll see what happens."
If she retains that opinion, Holmes will accompany Diane Modahl in the shorter distance at Atlanta. Modahl's second place on Saturday, in 1min 59.87sec, saw her make certain of a place just three months after being finally cleared of the doping charges, and only eight months after giving birth to her daughter, Imani - named after the Swahili word for hope.
Tessa Sanderson, who achieved the Olympic qualifying mark of 60m at the age of 40 last month, won the javelin title with a throw of 62.48m. She is gradually inching up towards the level of 65m at which a medal might be a possibility.
Curtis Robb, timing his return to form perfectly, retained his 800m title with a time of 1.47.61.Reuse content