Prince Harry, Meghan Markle, Prince William and Kate Middleton will appear on every TV screen across Britain tonight.
The royals will reunite to take over TVs across Britain in a film that will be broadcast simultaneously across all commercial channels.
They will feature in the short film at 8.45pm to 11 million viewers as voices of the major NHS mental health campaign.
They will promote Every Mind Matters – an NHS resource that will provide personalised advice for people struggling with stress, depression or poor sleep.
From today, millions of Brits can use the resource’s website to receive a tailored “action plan” containing clinically-proven steps to improve their mental health.
Tonight’s film was written by Love Actually director Richard Curtis and is narrated by the Duke and Duchess of Sussex and the Duke and Duchess of Cambridge.
It will feature celebrities including Davina McCall, Bradley Wiggins and Gillian Anderson, who will be talking about their own experiences of mental health problems.
Prince William will say: “All over the country, millions of us face challenges to our mental health – at all ages – at all intensities, and for all sorts of reasons.
“We feel stressed, low, anxious or have trouble sleeping.”
Meghan will say: “From today, there’s a new way to help turn things around.
“Every Mind Matters will show you simple ways to look after your mental health.”
The new NHS online platform has been endorsed by all major charities and leading doctors, and involves a short questionnaire asking about mood, sleep and any worries you have.
After filling in the questionnaire, people are given a tailored “mind plan” featuring practical tips and resources to improve their mental health.
For example, someone who is worried about money will be pointed towards local debt advice services. And people who sleep badly are given tips such as turning off their phone an hour before bed.
The royals will reunite in the advert tonight following months of claims of a feud between the Sussexes and Cambridges.
Meghan and Harry moved out of Kensington Palace, where they lived next to Kate and William, as the rumours reached fever pitch.
They then went on to break away from the Cambridges’ charity partnership as they formed their own charity, further fuelling the feud claims.
One of their lasts appearances together was at Trooping the Colour in June when they joined the royal family on the balcony of Buckingham Palace to watch the Red Arrows flypast.
But even on that occasion the couples stood apart on different sides of the balcony as the feud murmurs rumbled on.