The lights were switched off at Buckingham Palace on Saturday evening as the British Royal Family did their part to support Earth Hour.
Buckingham Palace was one of many landmarks across the world to mark the hour, which is all about protecting the planet and helping to reverse global warming.
Windsor Castle, Big Ben, the Eiffel Tower and Sydney Opera House also took part in the turning off of lights for the cause.
The Queen wasn’t in residence at Buckingham Palace during the electricity-free hour, although, it is likely she was sitting by the candle light in Windsor Castle, which also took part in the event.
Earth Hour takes place every year to remind people about saving electricity and to be more wary about the amount of electricity we use.
It is organised by the World Wildlife Fund (WWF) who encourage members of the public to take part in the hour in the comfort of their own homes.
The event was first marked in Australia ten years ago. A decade later and 100 countries now take part, with people including The Queen doing their bit to reduce pollution.
A spokesperson for WWF said: “It’s not about sitting in the dark for an hour.”
They added that it doesn’t matter how people spend the hour, just as long as the lights are out:
“Whether someone is enjoying their favourite book, getting together with friends for a candlelit dinner party or stargazing with loved ones, it’s their event too.”