On a day as cold and grey as Puritan steel a large crowd waits in Whitehall. It is the thirtieth of January 1649 and there are spectators everywhere, for this is a momentous event. Gentlemen lounge behind the balustrade that tops the Banqueting House, while ladies and servants lean from the windows. Some daring young men sit precariously on the roof.

The crowd is a motley mixture of people. City merchants in cloaks of good cloth murmur to their wives. A couple of country women, their shawls covering their heads, stand with baskets of eggs at their feet. A few gentlemen sit astride well-groomed horses, their ringlets and plumed hats suggesting that their sympathies lie with the King. A murmur of anticipation rises from the crowd, while a man comforts his sobbing son. Women shiver in the chill wind that blows across St James’ Park.

Beyond the curious populace, a ring of steel is drawn. Rank after rank of infantrymen stand immovable. Most carry pikes but a company of musketeers flanks the scaffold. On one side, troops of horse are lined up, the faces of the men clamped in grim steel helmets. The horses stamp and toss their heads. The New Model Army is demonstrating that they have the power now.

The sides and floor of the scaffold are draped in black, with the block placed in the centre. Dr Juxon, dressed in clerical black, holds the King’s cloak and his Order of St George. Colonel Tomlinson stands by in his role as the head of the guard.

All eyes are drawn to the figure at the heart of this tableau: King Charles. He kneels with his head laid on the block, his hair caught up in a cap and his arms stretched out to indicate that he is ready. His lips move in prayer. The masked executioner stands with his axe raised and, as the weak January sunlight strikes the edge of the blade, it lights a silver fire.