Breffni Martin, from Hartlepool, said she did not have the chance to write books while she worked full time in education.
She taught for 20 years at Dyke House School and a further eight at St Hild’s School before taking up other teaching posts in London and Sheffield.
But following her retirement, Breffni finally managed to combine her passions for history and writing fiction, with her first two books released in April and May.
The novels are part of a series called The Bretton Horse Warrior, with five more titles in the works.
The opening book, Ravensworth, is set in 1071 and follows Norman warrior Luc De Malvais, who is asked to control a large rebel area around the North Yorkshire village.
Breffni has described the book as a “page turner” with plenty of action and suspense.
She said: "It’s been very, very popular. It’s a good story, everyone keeps saying it should be a Netflix series.
"Everyone falls in love with the hero.”
The author says she has always been interested in this period and the “Harrying of the North” when Norman invaders burnt all villages between the river Humber and the river Tyne.
But Richmond and Ravensworth were spared, so Breffni started wondering why - and found it was because of Alan Rufus, who was King William’s nephew and built Richmond Castle.
Breffni said: “I thought ‘What must’ve it felt like to be a Saxon in those days when the Normans arrived.”
Breffni writes under the pen name SJ Martin in honour of her grandmother Sarah Jane Martin.
Following the First World War, Breffni’s grandfather travelled for work from the coal mines at Trimdon to the iron ore mines in the Cleveland hills.
Sarah Jane insisted the family should never be broken up so she and the children travelled with him as he looked for work.
She also insisted that wherever they lived there was always books in the house.
Breffni said: "My grandmother, who was 5ft10 was an amazing woman.
"She inspired me, even though I knew her only for a short while as a child, so I decided to use her name.”
Breffni’s next book will be released in June.
Copies are available via Amazon.