They may be used to quench the thirst of marathon runners but the Prince of Wales was very taken with another use for edible water balls – filling them with alcohol.

Charles came across the innovation during a visit to the Cool Planet Experience, a climate change-centred attraction in County Wicklow, where a group of children were learning how to make the environment-friendly alternative to plastic bottles.

The heir to the throne could not resist asking: “Does it work with whiskey?”

And when he was told they could be filled with any liquid, even gin and tonic, he replied: “Now you’re talking.”

During the first day of his visit to the Republic of Ireland, Charles also met some of the Cool Planet champions who are volunteers recruited by the attraction and trained by international leaders in the field of climate change.

They have been charged with the mission of spreading the message throughout Ireland through local communities.

Electrifi, an Irish car manufacturing company which specialises in converting high-end cars to run on electric batteries, showcased an electrified 1983 Range Rover to the prince.

Cool Planet chief executive Vicky Brown welcomed the visit, saying: “His Royal Highness’ visit to Cool Planet Experience not only signifies his appreciation for what we are achieving here but also reinforces our efforts to educate the next generation about climate change and how they can make a tangible difference.”