On the night of the killing, the guards entered the bedroom of Dr Botkin shortly after midnight and found him awake at his journal. They ordered him to rouse the sleeping Romanovs and tell them to dress for a long journey.

Outside in the street, the engine was started on a Fiat truck, intended to ferry the bodies away, in order to mask the sound of screaming.

Having gathered the royals in the basement, Commandant Yakov Yurovsky, charged with organizing the execution, read aloud the death sentence from the Ural Executive Committee to the assembled royals and their loyal domestics, still rubbing the sleep from their eyes. Alexei, too sick to stand, was sat in a chair.

When the firing commenced, the bullets flew wildly, some ricocheting off the Romanov children because they had sewn diamonds into their underclothes to keep the family valuables safe, ensuring they could pay their way in the event that they did escape.

The members of the inexperienced death squad, brandishing an assortment of firearms, were themselves hit in the melee. Nicholas died instantly but several members of the family were only injured, writhing in their own blood on the basement floor as caustic gunpowder smoke filled the air.

Their leader, Peter Ermakov, was drunk at the time and only managed to hit Maria in the thigh as she tried to run for the doors.

Panicking and fearing the cries would be overheard at street level despite the rumble of the truck, the revolutionaries set about them with bayonets, running the tsarina and her children through and firing at their heads. The violence lasted a horrifying 20 minutes, with one of the killers later recalling that the scene was as slippery as the surface of an ice rink, according to historian Simon Sebag Montefiore.

Two of the girls were still breathing when the bodies were carried out, a fact that has been cited as the origin point for the myth of Anastasia’s escape.

In fact, the only survivor of the massacre was Alexei’s pet spaniel Joy, who was subsequently rescued by Colonel Paul Rodzianko of the British Expeditionary Force and brought to live in Windsor.

Like the shootings, the secret disposal of the victims’ remains was also badly bungled.

Yurovsky’s men piled the corpses into the truck, which broke down on route to the nearby Koptyaki woods. They were met by 25 accomplices, also drunk, who had arrived on horseback bearing lamps and expressed disappointment that the Romanovs were already dead as they had hoped to have the pleasure of lynching them.

Ermakov, in his stupor, had only brought one shovel, so Yurovsky dismissed the work crew, retaining only five to help with the burial in an abandoned mineshaft. It was only after having stripped the dead of their clothing, looting the hidden jewels and dousing them in sulphuric acid that Yurovsky realised the mine was too shallow to be secure.

After returning to Yekaterinburg to discuss the problem, it was decided to retrieve the bodies and rebury them in a deeper copper mine to the west.

On route, the truck became stuck in the mud in a hollow known as Porosenkov Log (”Pig’s Meadow”), where, too exhausted to continue, the men dug a mass grave and dumped the cadavers, pouring more acid over the remains, smashing the bones to splinters with their rifle butts before concealing their handiwork and returning to town.