For years, Mwangi and his fellow constables had been able to doze through their night duty without any fear of disturbance. In recent months, however, the white farmers and their families had seen the Mau Mau in every shadowy movement in the night and had heard their approach in every unexpected noise. Barely an hour earlier, he had answered the phone to hear a terrified white woman pleading with him to come to her aid.

‘They’re out there, the rebels – I know they are, the murderous swine. I can hear them and I’m all alone, my husband’s away in Nairobi. Come here now, boy, now!’

Mwangi had driven out to her farm, a couple of miles from the police station, to find a loose tool shed door being tapped against its frame by the gentle breeze, and an empty oilcan rolling across a patch of stony ground.

Mwangi had taken the woman’s hands in his, looked into her eyes and said, ‘There are no bad men out there, memsahib. I promise you this. I have checked for myself and I know it to be true.’

Back at the station, Mwangi had another duty to perform. Every two hours, he was required to leave the station and patrol the blockhouse perimeter. He looked up at the clock on the wall opposite his desk. It was time for his patrol.

He put on his cap, picked up his torch and walked out of the police station and across the bare earth towards the gate. In the bright light from his torch he could see that it was closed and the chain was locked in place.

Mwangi continued for a further twenty paces or so. The torch beam played back and forth casually, the sign of a sentry who does not expect to see anything out of the ordinary. Then he stopped. Something was wrong.

He examined the fence again, more carefully. The beam illuminated a void: the empty space where wire no longer ran. Someone had cut their way in.

The police in Kenya, like those in Britain, were not routinely equipped with firearms. Mwangi had only a truncheon to defend himself as he ducked through the hole.

He stood up. Now his torch was shining on solid concrete walls.

Mwangi began a circuit of the blockhouse.

He was halfway round when he saw them: five men crouched beside the steel door.

Every one held a panga in his hand. They looked at him with cruel, merciless eyes.

Kabaya stood up, pointed to Mwangi and said, ‘You’re late.’

Maina Mwangi was another war veteran. His application to become a policeman in 1946 had been accompanied by an exemplary record of military service and a glowing testimonial from his former CO. But he, like Kabaya, bore a deep and abiding grudge against the British Empire that had been so willing to use his people in war, yet reluctant to respect them in times of peace.

Mwangi grinned as he handed over the key to the blockhouse.