Jackson, fully recovered from the back spasms which forced him to scratch from the world championship semi-finals last year and subsequent surgery on his left knee, has made a steady rather than spectacular start to the season, and until Friday night his training partner, Mark McKoy of Canada, had run faster than him despite the fact that they were doing the same work.
But as Jackson pointed out last month, he had not found himself in fields of the same quality as those McKoy had entered. 'I'm going to start running fast very soon,' he said. 'I'm feeling as good now as I did when I won the Commonwealths in 1990.'
Crystal Palace provided him with the opportunity to prove it with an event that called on six from the top eight world-ranked high hurdlers this year, including the world champion, Greg Foster, and all three US representatives in Barcelona - Tony Dees, Arthur Blake and Jack Pierce. His winning time, registered briefly and erroneously by the photo-finish clock as an apparent world record of 12.83, was 0.02sec faster than he had achieved in Auckland. But it is the knowledge that he has beaten America's best that will sustain him most in the coming fortnight.
Would that the same could be said for Black. There would be no more popular medallist than he at the Games: 'Mr Sex on Legs', as his mate Kriss Akabusi joshingly calls him, started up his own official fan club last week to cope with the weight of interest. But as he laboured home in fourth place behind Michael Johnson's phenomenal all-comers' record of 43.98, gold, silver or bronze in Barcelona looked a very long shot.
Black's explanation afterwards was about as direct as they get. The hip injury which has been troubling him for the last three weeks was not a factor. He felt OK. He tried to keep up with Johnson and the Olympic champion, Steve Lewis, who finished second in 44.55. He could not.
'I saw Michael just sort of jogging at 300, which is quite demoralising,' he said. Did he think the Americans - three of whom have now gone under 44sec this season - had peaked too soon, someone asked hopefully. 'No. They always know what they are doing. It would be silly to say things are looking great for Barcelona because obviously they are not. To say I am optimistic would be wrong. I am realistic.'
At last month's UK Championships, where he won in a highly promising 44.84sec, Black indicated that he hoped to be running around 44.50 now to be in contention for a medal. His last three races, in varying conditions, have yielded three times over 45sec.
'It is strange that I can run 44.84 on a windy day in Sheffield and only manage 45.19 here,' he said. 'I just have to produce something extra. There's enough time. Things can change fast in this game.'
Something extra fast turned up in the 1986 European Championships, where he improved by half a second to win the title. 'It hasn't happened much in the last few years, though,' he added glumly.
Now Black must hope for some encouragement in Nice on Wednesday, when he runs his last 400m before Barcelona. The fact that he will not have to face Johnson there - the world 200m champion having elected to concentrate on the shorter distance for the Olympics - is cold comfort.
Johnson's words were as demoralising as his deeds. 'My whole career is based on being the best in the world at both 200 and 400m. Just because I have chosen to do the 200 in Barcelona doesn't mean I can leave the 400 alone and let the other guys have it.'
And for all that the Texan was just keeping his hand in, he was strongly critical of what he claimed were Black's efforts to get on a lane inside him. 'I couldn't run in lane two, which I like to do, because Roger said I always keyed (paced himself) off him. For the record, I do not key off Roger. He goes off too fast and then dies. Even if he can get things changed here, he is going to have to handle it everywhere else.'
Johnson is an impressively cool and articulate customer, but his defeat over 200m in Rome last month shows he is at least capable of being beaten. 'Everybody gets beaten some time,' he said. 'Frank (Fredericks) just ran a better race that day and that can happen.' Black had better believe it can happen for him, too.
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