THE Commonwealth of England has had short shrift from school curriculum planners.
It's as if our 11 years as a republic then dictatorship is somehow not "proper" history. Class, we've done the beheading of King Charles I in 1649. Now reopen your textbooks at the restoration of the monarchy in 1660.
That may have something to do with traditional teaching methods, believes historian Charles Spencer.
"Young people were taught history at school in terms of the reigns of kings and queens," he says. "I studied Charles I and the English Civil War but I knew nothing about the Commonwealth that followed it."
The writer – known more formally as the 9th Earl Spencer – has put that right. His research into the Interregnum and Restoration has resulted in the book Killers Of The King.
Spencer was in Nottingham this week to sign copies at a private dinner at Hart's Restaurant – situated on the very hill where, in 1642, Charles launched his catastrophic war against Parliament.
Catastrophic not only for king but also kingdom. Some estimates put the number of combat deaths at close on 100,000, with countless thousands more civilians perishing of plague and famine. It remains the bloodiest war on British soil.
Spencer's book concerns the aftermath – the fate of the 59 commissioners who convicted the king and others associated with his downfall and death.
When his son King Charles II claimed the throne in 1660, nine surviving regicides were executed and several were sentenced to life imprisonment; some remained in exile, fearing death if they returned.
Spencer's book charts the Stuart revenge and the author has sympathy for the hunters who became the hunted.
"When I began my research, I thought I would feel sorry for Charles," he said. "A nice man, a devout Christian, a good father. But I grew to feel he was a terrible king. He always followed the advice of the last person who spoke to him.
"He was still ruling in a medieval way even though the time had passed for Parliament to have a bigger say.
"You have to respect the motives of those who signed the warrant – they were very principled and sincere."
The concept of the Divine Right of Kings, struck a near-fatal blow at Whitehall in 1649, expired with the Glorious Revolution of 1688.
The concept of constitutional monarchy developed over the next three centuries and, as brother to the late Diana, Princess of Wales, the author is uncle and great-uncle to princes who will sustain that tradition.
Charles Spencer, 50, was educated at Eton and Oxford, where he read modern history. The father of seven children, he lives at Althorp, the Spencer estate in Northamptonshire, with his third wife, Karen, Canadian-born founder of the charity Whole Child International.
He succeeded to the earldom in 1992. Five years later, at Diana's funeral service, he dropped the world's jaw with a eulogy including criticism of both the media and the Royal Family. In happier days, his literary reputation has grown. There were early books about Althorp and the Spencer dynasty but his breakthrough as a mainstream historian came with Blenheim, Battle For Europe (2004); the victor of Blenheim, the Duke of Marlborough, was great-grandfather of the 1st Earl Spencer.
The author's work is done in a special room at Althorp. "My study is my grandmother's sitting room," he explains. "I was eight when she died but I remember her very well.
"It is very much 'her' space but I find it allows me to be creative. It has high windows and the light streams in. I can do about four hours of research every day but if I do much more, it's like running down a battery – I struggle to do four the next day.
"My wife is Canadian, so is not so familiar with English history. I am always reading to her what I have written and she says, 'It sounds like fiction – it's going at such a pace'!"
Killers Of The King is pacey, not racy. The author rejoices in disclosing telling detail about the lives of the men and women whose actions changed the course of history.
Look out for characters like the louche Notts barrister Gilbert Millington; Attenborough-born cavalry general Henry Ireton; John Hutchinson of Owthorpe, redoubtable governor of the Nottingham Castle garrison, and his loyal wife Lucy (see panel).
Spencer is currently looking at three possible projects but knows he must be able to sustain his passion for whichever one he pursues.
He quotes another descendant of the Duke of Marlborough, Sir Winston Churchill. "Writing a book is an adventure," observed the great war leader, who won the Nobel Prize for Literature. "To begin with it is a toy and an amusement. Then it becomes a mistress, then it becomes a master, then it becomes a tyrant."
Don't be surprised if one day Spencer returns to familiar territory. "The English Civil War," he reminds us, "is so fundamental to what this country is today."
Killers Of The King – The Men Who Dared To Execute Charles I, is published by Bloomsbury at £20.