Grace Mandeville, British web and television actress who stars as Holly in the TV series The Sparticle Mystery. She and her sister Amelia run a YouTube channel together called Mandeville Sisters. She began her career in television in 2011 when she first started appearing in The Sparticle Mystery. She and Amelia create funny vlogs on their channel and also run a lifestyle, food, fashiom and travel blog. She and Amelia have a younger brother named Henry. She and Karim Zeroual are both featured in The Sparticle Mystery. ^[1]