Prince William was unable to attend the 2022 Earthshot Prize Innovation Summit in person on Wednesday, but he made sure to record a special message.

The Prince of Wales lost his grandmother, the Queen, on September 8, and the royals are currently in a period of mourning following her funeral on Monday.

Referencing the late Queen, William shared in a video call Wednesday: “Although it is the saddest of circumstances that means I cannot join you in person today, I am pleased to join you in video form as you gather in New York for the Earthshot Prize Innovation Summit.

“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.”

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He went on, “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.”

William said that although the world is an “uncertain place right now,” there was a “huge reason to be optimistic.”

He told viewers, “The 2021 cohort of Earthshot Winners and Finalists is evidence that we can succeed. That we can protect our world for our children, our grandchildren and the generations that will follow them. These pioneers exemplify the leadership needed in this decade of change. They include inspiring activists, brilliant innovators, a forward-thinking city and even an entire country making a real difference. But they cannot do it alone. This must be a team effort.”

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He concluded his speech by saying that he and wife Kate Middleton “are so excited to be coming to Boston in December. We look forward to seeing you all very soon,” discussing the second Earthshot Prize awards ceremony’s location.

William and his charity, The Royal Foundation, launched the prize in 2020 inspired by U.S. President John F. Kennedy’s 1962 “Moonshot” speech that challenged Americans to go to the moon by the end of the decade.

The prize, to be awarded to five winners every year until 2030, is billed as the most prestigious of its kind. Each winner will receive a grant of 1 million pounds (around $1.5 million) to develop and scale up their ideas to help the environment amid the climate crisis.