Prince William, Rio Ferdinand and Mary Berry are among the celebrities to join forces with bereaved families to discuss grief.
In a series of videos for charity Child Bereavement UK, they discuss what they would do if they had just one more minute with someone they had lost.
The films also include children, parents and a bereaved couple.
One opens with a young boy, who tells the camera: "If I had one more minute, I would tell her: ‘I still wanted you to be with me'."
In another clip, a mother whose child was stillborn says: "I think it would be nice to look at her, to see her open her eyes."
The charity's chief executive, Ann Chalmers, said she hoped the campaign would help people understand the impact of bereavement.
The advert will air on Channel 5 at 8pm on Friday, and people are also being urged to share their own 'One More Minute' films to social media under the hashtag #onemoreminute.