Prince Harry is said to have been left distraught after the death of his friend and mentor Jules Roberts.

The Duke of Sussex sent a private note and flowers to the funeral of Roberts, who first met the prince in 2013 to train him ahead of his South Pole trek, The Mirror reported.

According to reports, Roberts helped Harry prepare for the trek, showing him how to haul sledges and survive in freezing polar conditions. Part of the training regime reportedly included spending 24 hours in an industrial freezer.

Roberts and the prince were said to have hit it off right away and developed “mutual respect”.

Following the training, the prince embarked on the trek in December 2013 to raise funds and awareness for the military charity Walking With The Wounded. He and his teammates covered around 320 kilometres in Antarctica through heavy sledges and temperatures as low as -45 °C.

A source said the prince was “very upset” upon hearing the news of Roberts’ death. “This has come as a real shock,” the source said. “Harry and Jules hit it off from the moment they met.”

Roberts died on August 5 at the age of 37 and was later cremated in Staffordshire. He is survived by wife Francesca and their two-year-old daughter.

Walking With The Wounded founder Ed Parker paid tribute to Roberts on Friday. “He was a properly good person with an energy beyond what you could imagine,” Parker said.

“I know that he admired hugely Harry’s commitment to both mental health and the veteran community. There was a lot of respect both ways.”