Josh Kerr made history at the London Diamond League, running 3:42.66 to break Hicham El Guerrouj’s legendary world record in the mile (3:43.13) from 1999.

Kerr, a two-time Olympic medalist from Great Britain, announced his plans to go after the record in March, and since then, he’s steadily built anticipation for the event. Every step of the process was done with intention. He structured his season to peak for the race. He chose London because he wanted to race in front of a home crowd. His sponsor, Brooks, created a bespoke pair of spikes and speedsuit for him, specifically designed for the record attempt.

…one thing was for sure: Kerr knew he was fit enough to break the record.

By unveiling the attempt four months before the race, there was a risk that things could go wrong. But one thing was for sure: Kerr knew he was fit enough to break the record. At the pre-race press conference, a reporter asked Kerr if there was a specific training session that made him believe the world record was possible.

“I believe at 6pm or 7pm tonight, you guys will get a little treat,” Kerr said with a cheeky grin. That “treat” turned out to be a video on Kerr’s YouTube channel titled “World Record Time Trial.”

In the video clip, the Scotsman is paced by Brooks Beasts teammate Brannon Kidder during a 1200-meter time trial (three laps of a 400-metre track). The session, which took place on July 3, was the “biggest workout of the build-up,” according to the video’s description.

Kidder and Kerr averaged 55-second laps for the first 800 metres – right at mile world record pace – then Kerr took over for the final lap, closing in a ferocious 51.88 seconds.

His final time, 2:42.45, is unofficially the fastest 1200 meters in history.

What made it even more impressive was that Kerr ran the time trial in Albuquerque, New Mexico, which sits at about 1,615 metres of elevation, meaning he likely could have run a few seconds faster at sea level.

At this point, Kerr knew he was ready. After the workout, he walked around the track amped up, noting that he only needed a 60-second lap to break the world record (plus another nine metres to account for the full 1609 metres in a mile).

“You think I can’t run a 60 right now?” he joked. Kidder, who would go on to pace Kerr through 800 meters in 1:50.70 on Saturday, was equally as hyped. “Holy shit, dude. You got it.”

Despite announcing the world record attempt in March, Kerr has raced sparingly during the outdoor season. He ran two good-but-not-earth-shattering 800-metre races in May and June, but he never lined up for a competitive 1500 or mile, instead prioritising a long training block.

But the 1200 was hard to ignore.

Even Tim Hutchings, who called Kerr’s race on Saturday on the world feed, admitted that the 1200-metre time swayed his view on Kerr’s chances. “I must admit, that turned my opinion,” he said, moments after Kerr broke the record. “I was 50/50 that he would get this today. And then I heard that he ran [2:42] for a 1200 and I thought, ‘No, it’s 75 percent likely now.’”

At the end of the YouTube video, Kerr says he wanted to walk away from the time trial like it was no big deal.

But after taking down one of the most iconic records in the sport, he deserves to celebrate like it’s 1999.

This article first appeared on the Runner’s World USA website.

READ MORE ON: josh kerr mile world record world athletics