The Prince of Wales has spoken of the “great comfort” he has taken in the enthusiasm of those supporting an environmental prize he founded, in a message recorded a day after the Queen’s funeral.

William had been due to travel to New York to attend an Earthshot Prize innovation summit as a countdown to the awards being staged in the US.

But he described the “saddest of circumstances” following his grandmother’s death, as he and his family continue to observe a period of mourning for the late monarch.

William was to make the solo trip to the United States on September 21, where he would have been joined by previous winners of his £50 million global environmental competition.

In a video, recorded on Tuesday at the Windsor Estate and broadcast on Wednesday, the prince said he believed the Queen would have “been delighted to hear about” the summit.

In a virtual message to those gathered in New York for the event, William said: “Though it is the saddest of circumstances that means I cannot join you in person today, I am pleased to be able to join you in video form as you gather in New York for the Earthshot Prize innovation summit.”

Protecting the environment was a cause close to my grandmother’s heart

He added: “During this time of grief, I take great comfort in your continued enthusiasm, optimism and commitment to the Earthshot Prize and what we are trying to achieve.

“Protecting the environment was a cause close to my grandmother’s heart. And I know she would have been delighted to hear about this event and the support you’re all giving our Earthshot finalists, the next generation of environmental pioneers.”

The royal family is continuing its period of mourning for the Queen, to be observed until seven days after the funeral.

Members of the royal family are not expected to carry out official engagements, and flags at royal residences will remain at half-mast until 8am on Tuesday – after the final day of royal mourning.

The Earthshot Prize was founded by William and his Royal Foundation in 2020, and in July this year the project became an independent charity, with the prince as its president.

The second Earthshot Prize awards ceremony is set to be held in Boston in December, after the inaugural event at London’s Alexandra Palace last year.

William said both he and the Princess of Wales are “so excited” to travel to Boston.

He last visited the US in 2014 when he travelled to New York with Kate, who was then pregnant with Princess Charlotte, for a three-day tour.

In his message, William acknowledged that the world is “an uncertain place right now”, noting that many people “are facing unimaginable challenges – from conflict to energy crises and food shortages”.

He said: “While addressing these in the short term, we must also remain resolutely focused on tackling the greatest challenges that threaten our tomorrow.

“Because if we don’t, the changing climate will only serve to entrench these immediate challenges into fundamental global issues, severely impacting the lives of each and every one of us. That is why our collective mission is so urgent.”

But striking a more optimistic tone, William insisted that “we can protect our world for our children, our grandchildren and the generations that will follow them”, citing last year’s cohort of Earthshot winners and finalists, who he described as “inspiring activists” and “brilliant innovators”.

We must collaborate in new ways, and we must be courageous

Urging people to work together, he called for a “team effort”, adding: “We must come together behind their innovative solutions to ensure they reach their full potential with pace and scale.

“We must collaborate in new ways, and we must be courageous.”

William said the Earthshot decade “must inspire action, creativity and collaboration around the globe” and called on people to “ensure the transition to sustainable solutions is the fastest and most endemic change the world has ever known”.