The One Direction star set social media alight on Friday (06May16) by posting an image on Instagram of himself holding a cut-off ponytail.

He captioned the image, "Whoops," and added the hashtag, "#Littleprincesstrust".

The Little Princess Trust is a charity which encourages people to donate their hair after they've had it cut so it can be made into wigs for child cancer sufferers who have lost theirs due to chemotherapy.

Co-founder Wendy Tarplee Morris confirmed on Tuesday, Harry had shorn his locks for the charity and raised much needed awareness of their cause.

"We didn't (know about Harry cutting his hair before he did it)," Wendy tells British daytime TV show This Morning. "Of course we were ecstatic when it happened."

Apparently it was the 22-year-old pop star's idea to donate his hair to the Trust, a Wendy revealed, adding, "A little while back his management team contacted the charity and said he'd expressed an interest in supporting us.

"So we gave some information and details to them and it was left if anything were to happen, they would come back to us. And then on Friday, it all happened."

According to Wendy, who founded The Little Princess Trust in memory of her daughter Hannah, who died from the disease aged five, the Steal My Girl singer's hair will be on its way to the charity very soon.

"It hasn't arrived yet - but there are plans in place to get it to us safely," she reveals.

Harry had to lose his famous long hair before he takes on his first acting role, in Christopher Nolan's World War II film Dunkirk.

The movie will tell the story of the 1940 evacuation of British soldiers across the English Channel in a flotilla of naval and civilian vessels to prevent their capture by Nazi troops.

In preparation for the shoot Harry will reportedly have to live on a ship for several days alongside co-stars Tom Hardy, Mark Rylance and Cillian Murphy in order to experience the conditions World War Two soldiers faced.

Filming on the project is set to begin on Saturday (14May16), with Dunkirk scheduled for release in July 2017.