Afghanistan veteran Duncan Slater has made history after becoming the first double leg amputee to complete the "toughest race on Earth" across the Sahara desert.

He and best friend Chris Moore crossed the finish line to end a gruelling 250km journey - the equivalent of six marathons - in fierce heat.

Moore was in the same convoy in Afghanistan when Duncan's vehicle was hit by a roadside bomb in 2009.

ITV News Correspondent Dan Rivers, who has been tracking Duncan's epic journey in Morocco, captured the moment the pair crossed the line.

Duncan's achievement was quickly hailed by Kensington Palace with Prince Harry following the progress of the injured hero he had journeyed with to the South Pole in 2013.

Duncan's wife Kim and daughter Lily had willed him on as they tracked him all the way to the finish line during the final day.

It was seven-year-old Lily's message that had helped inspire her father to keep up his heroic effort on the eve of the final day.

Duncan said her message that he "can do it" was "mega" at a point in the race when his body was failing him.

Chris and Duncan shared an emotional embrace after completing the distance. Credit: ITV News/Dan Rivers

Duncan battled a hamstring injury and total exhaustion but refused to quit the Marathon des Sables through the desert.

Rivers said he faced worsening weather on the final day.

Duncan had previously made history as the first double leg amputee to reach the South Pole. Credit: ITV News/Dan Rivers

"It's been incredibly windy today," he said. "Sandstorms (have been) blowing into his eyes all day - combined with the fact that he's also been really ill with heat exhaustion overnight - (but it) hasn't stopped him."

Duncan's last day started with drama. After vomiting with severe dehydration overnight, he headed back to the start line for the final day on an empty stomach.

Duncan Slater has faced temperatures touching 50C as he scaled giant sand dunes. Credit: ITV News

Duncan came agonisingly close to finishing last year's race, but had to pull out on the last days due to severe chaffing on his stumps.

His successful effort this time came on new high-tech prosthetic legs made in Italy.

Fellow Afghanistan veteran Chris Moore remained at Duncan Slater's side throughout. Credit: ITV News

Duncan became the first double leg amputee to ski to the South Pole, a challenge that saw him share a tent with Prince Harry.

The royal had wished him well during a surprise visit captured by ITV News during training for Marathon des Sables.

The pair made a brief stop under shade en route to the finish line. Credit: ITV News