Jack Greaves biography Jack Greaves is a London-based actor and musical theatre performer. Born in Northumberland, England, the British actor is also a studio fitness instructor. Jack will make his West End debut by performing in the hit musical The Book of Mormon. Training: He received his professional training from the Bird College of Dance. Theatre: His theatre credits include swing in The Book of Mormon, cover Michael Wormwood in Matilda the Musical (Cambridge Theatre), cover Rusty Caboose, Flat Top, Hoppers, National Engines, Components in Starlight Express (Bochum, Germany), ensemble and cover Billy Goose in Mother Goose (Hackney Empire) and Gideon in Seven Brides for Seven Brothers (No.1 UK Tour).