Trease, who died last week aged 88, decided to show children the past as it really was. He fascinated them with dozens of adventure stories set in real historical situations.
From childhood, he was determined to become a writer. While his brothers excelled at football and cricket he stayed at home scribbling stories. When he won a junior scholarship to school at 13 his father asked him whether he wanted a bicycle or a cricket bat? He chose a typewriter.
He later started a degree at Oxford but found it too dry and academic so abandoned his course and headed for London.
Geoffrey Trease spent his days working as an unqualified teacher while at nights he slaved at the typewriter but with little success. His first breakthrough as a children's writer came with the novel Bows Against Barons published in 1934 - a realistic version of the Robin Hood story that portrayed the harsh life of the poor in medieval days.
The novel was in print for more than half a century. It was published in 10 countries and helped institute a revolution in British children's literature.
In 1940 Cue for Treason appeared. It was to become his most popular and successful novel and was particularly significant because of the balance between the parts of the hero and heroine. Set in the Shakespeare's day it portrayed a company of strolling players plotting against Queen Elizabeth I.
Trease produced more than 100 books in a career spanning more than 60 years.