Moore struck a chord with locked-down Britain, and made headlines around the world, by walking around his garden with the help of a frame to raise 38.9 million pounds ($53 million) for the National Health Service.

His death in February drew condolences from Queen Elizabeth, Prime Minister Boris Johnson and Joe Biden’s White House. The news was reported across Europe, the United States, Asia and beyond.

One year on from the day he started his walk, his family are inviting people around the world to come up with a challenge around the number 100 and complete it over the April 30 to May 3 Bank Holiday weekend, marking Moore’s birthday.

Examples given include writing a 100-word poem or telling 100 people the line that became Moore’s catchphrase: “Tomorrow will be a good day”. Proceeds could go to the Captain Tom Foundation or any charity of choice.

“This is about whoever you are, whatever circumstance you are in, invent your challenge around the number one hundred,” Moore’s daughter Hannah Ingram-Moore told Reuters. “You imagine if he was still here, he would just be thinking this was the best thing ever.”

Hannah said her father had become a beacon of hope at a dark time. Having set out to raise 1,000 pounds, he raised almost 40 million in just under a month. In 10 days he had received 1.5 million emails. His 100th birthday was marked by the arrival of 200,000 cards.

“He left us with this incredible gift of hope,” she said of a man who became known for his wit and positive outlook. “We know that his voice of hope for the world resonates.”