Reader was born in Crewkerne, Somerset, England, the son of a Salvation Army bandmaster. He was orphaned by the age of eight, and brought up by aunts and uncles. Joining the Scout Movement at the age of eleven, he began his theatrical career by putting on Scout Shows as a Patrol Leader in the 2nd Newhaven, Denton and Heighton Troop in Newhaven, Sussex. His first job was as a delivery boy for a relative's greengrocer's shop in Seaford. He would be taken by his employer to Brighton to buy supplies, and then visit the Hippodrome theatre, where he saw many of the music hall stars of the day. At 14 he became a telegram messenger and at 15, an office boy at a cement works.