The French athlete produced a phenomenal laser-run showing to take the gold medal on 1,280 points ahead of Italy's Alice Rinaudo and Elzbieta Adomaityte of Lithuania.

Castaudi was 21st to begin the final discipline, 49 seconds behind leader Rinaudo, but surged through the field to claim a dramatic victory.

"I feel very, very good - I never felt so good in my life," Castaudi told the UIPM website after the win.

"It’s an immense joy and satisfaction for me, I trained hard for this all year and this is the outcome so I am very happy today.

"The run was definitely my best discipline. 

"I gave everything."

None of Castaudi's fencing, riding or swimming scores were in the top 10 - but such was the quality of the laser-run, the 20-year-old won.

"I aim for Paris 2024," Castaudi added.

"Next year I join INSEP, so it is really to aim for the Olympics, it makes me very happy and I am looking forward to it and training."

Castaudi had qualified for the final in impressive fashion, scoring just one point fewer than the field's highest total.

It is Rinaudo's second silver medal of the UIPM Junior World Championships, following a second-place finish in the women's relay on the opening day.

The Italian overtook Adomaityte late on as the latter struggled with exhaustion.

Rinaudo was 12 seconds behind the winner, Adomaityte 15, with scores of 1,268 and 1,265.

Hungarian Rita Erdos was fourth and Anna Jurt from Switzerland fifth.

The men's final is scheuled tomorrow at the under-21 event.