The Canberra athlete was "in gold medal position" last year before the Tokyo Paralympics was swept from under him. A torrid four-month battle with injuries ensued.

But Roeger has put those lingering doubts to bed with a T46 world record at Athletics Australia's Tokyo qualifying marathon in Sydney on Sunday.

The feat marks Roeger's fourth consecutive world record in a marathon, this time crossing crossed the line at 2:18.52 to slash a staggering 40 seconds off his personal best.

Perhaps just as remarkable is the fact his pacemaker Jaryd Clifford set the world record of 2:19.08 in the T12 class for vision impaired athletes - and he originally had no intention of finishing the course.

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Now both men will set their sights on the Paralympics, with ACT-based Roeger chasing a maiden gold medal in the marathon in what will mark his fourth appearance at the Games.

"I'm really happy with that. I got a 40 second PB and world record and that gives me a lot of confidence leading into the Paralympics in August and September this year. Hopefully I'll stand on top of the podium and sing the national anthem proudly," Roeger said.

"I wasn't quite confident in that last six kilometres. My legs were cramping but I just had to hold it together. Now I've got 2:18 next to my name, and that's giving me loads of confidence in these last few months of training.

"I'll now reset and respect the distance and then do the Gold Coast Half Marathon, and then it's all roads to Tokyo."

Clifford and Saunders ran as pace-setters for Roeger. The latter had such little intention to finish the course he can't even remember his last long-distance run.

Just last week he was part of a 4 x 400 metre relay team at the university nationals. Now he has shaved almost two and a half minutes off the world record in his class, musing "I feel a bit silly now having broken that world record".

"I came out here and just wanted to get Roegs as far as possible. I think he asked me at 15km how many laps I had left in me, and I think I said I had two. Then I had one more, and then another," Clifford said.

"I feel a bit silly upon reflection, but I think psychologically all I was doing throughout the race was focus on Roegs who is going for the gold medal at the Paralympics in Tokyo.

"I was telling him in the last 10km that this was for the gold medal in Tokyo so all he has to do was run as hard as he can and he'd win a gold medal for Australia."

The Paralympics begin on August 24 and run until September 5, taking place a year later than originally anticipated due to the outbreak of the COVID-19 pandemic.

But coach Saunders is confident both Roeger and Clifford can rebound to claim gold in a landmark moment for Australian athletics.

"Tokyo getting cancelled was a big deal. They were in gold medal position and then that got taken from under them," Saunders said.

"Roegs couldn't run for four months [due to injuries] and we didn't know if he'd be at the same level again, so this marathon was massive for us.

"This run is something that has given him confidence to win that gold medal, his first Paralympic gold medal at the Games. We had a big pacing team behind him, but two got injured so Jaryd and I stepped up to try and get him as far as we could. The way it played out was amazing.

"Jaryd has been training for the 1500m, and today shows his potential for the marathon. These are two of the best athletes Australia has ever seen and they're going to be standing on top of the podium with gold medals for Australia."