Jayden Sawyer has amazed himself with a towering world-record throw to win a javelin gold medal at the world para-athletics championships in London.

"Where did that even come from?" asked the 23-year-old from Canberra after exceeding his personal best by 4.5 metres with his winning throw of 52.96m.

Sawyer's effort was just one highlight for Australia on the penultimate day of the world titles as Deon Kenzie won a maiden world title in the 1500m T38 event and wheelchair racer Madison de Rozario also claimed gold, winning the 5000m T53.

Sawyer, 23, placed fifth at the Rio Paralympics last year but felt the big throw for his first world title was reward for his preparation.

"I knew I was in a good place and I have been working on my run up. It was just a matter of relaxing," he said.

"My coach Mike (Barber) and I always knew I was capable of doing it, it was just a matter of backing myself and being confident in that."

Kenzie (Tas), who has cerebral palsy, ran a well-executed race to win in 4:06.68, moving swiftly past France's Louis Radius and Tunisia's Abbes Saidi and increasing his lead with each step in the last 200m.

"That's bronze in Lyon (2013), bronze in Doha (2015), silver in Rio and now gold in London," Kenzie exclaimed.

De Rozario (WA) was forced to battle hard for her second medal of the world titles.

"The whole time I kept coming in and out of the lead, and I was worried I had my main lead too early in the piece. All the big screens around the stadium helped so I could look back and see what was happening," de Rozario said.

Wheelchair racing great Kurt Fearnley (NSW) qualified for the final day's 5000m T54 final, after finishing second in his heat.

The four-time world champion admitted it would be a huge challenge to win.

"You get in these finals, and you have no idea of how things will go. It will come down to the last lap, that's for sure," he said.

AAP