The Duke of Sussex is competing in a Sentebale polo match on Thursday after donating 1.5 million dollars (£1.1m) from the proceeds of his upcoming memoirs to the charity he co-founded.

Harry will be joined on the field in Aspen, Colorado, by Argentine polo player and Sentebale ambassador Nacho Figueras.

The royal family is braced for the publication of Harry’s memoirs next year which he has written “not as the prince I was born but as the man I have become”.

Harry set up Sentebale, in memory of his mother Diana, Princess of Wales, in Lesotho in 2006 to help vulnerable children in southern Africa affected by extreme poverty, inequality, and the HIV/Aids epidemic.

The Sentebale ISPS Handa Polo Cup was postponed last year because of the pandemic.

Harry said he was thrilled to be supporting Sentebale in person and his donation was one of several he planned to make to charitable organisations.

The duke said in a statement on the charity’s website: “Our refocused mission at Sentebale is about addressing the most-immediate needs of vulnerable children in southern Africa, helping them access vital health services, receive necessary care, and build skills to be more resilient and self-sufficient in the future.”

He thanked sponsors and those who had helped to make the tournament, which will have fewer guests than normal, Covid-safe.

The duke added: “The Sentebale Polo Cup is critical to securing the funds needed to advance this important mission, and I’m thrilled to be able to support Sentebale, both in person and financially through a separate charitable donation to meet this immediate need.

“This is one of several donations I plan to make to charitable organisations and I’m grateful to be able to give back in this way for the children and communities who gravely need it,”

The duke will play on the Sentebale Team against the Royal Salute and US Polo Assn teams in a round robin tournament.

Sentebale said the match was its single largest fundraising opportunity and its postponement last year left the charity in need of further support, with Harry stepping in to help.

“Because last year’s Polo Cup was postponed and this year’s was significantly and rightfully reduced in size and scope, the organisation is in need of further support to continue its mission,” it said.

“To help meet this need, the duke is donating his time as well as honouring his personal commitment to donate a portion of his proceeds from his upcoming memoir by generously committing 1.5 million dollars to Sentebale.

“Sentebale is grateful for his personal contribution, which will allow the organisation to continue operating at full scale and continue providing critical services to at-risk youth in southern Africa.”