‘Fire escape as far as the third floor,’ said Joe, ‘but then it gets a bit tricky. It’s a fingers and toes job up the next floor and then there’s the ledge overhang to negotiate before he can inch his way along to the broken window. Not pleasant but it has to be done. Heaven knows what clues, what evidence he might have left behind. Well, you know . . . button, thread of fabric . . . identity card?’

‘Found a pair of false teeth at the scene once!’ said Cottingham jovially. ‘Clamped around a beef and horseradish sandwich, they were.’

Armitage handed his cap to young Sweetman and began to take off his jacket. His usual swagger was absent, Joe noticed, as he said, ‘Leave this to me, sir.’ He clenched and unclenched his large hands and the knuckles were white with tension as he scanned the façade.

‘Stand down, Sergeant,’ said Cottingham. ‘No need for that! Constable Sweetman is here for a purpose. Not just a pretty face – the lad has hidden talents, I’m told. Rock climber at weekends! You may divest yourself of your helmet and tunic before commencing, Roy, if you wish.’

The constable grinned and cast an assessing eye over the climb. ‘It’ll be a doddle, sir. Shall I start now? Is anyone going to time this?’

Cottingham took out a stop watch and moved off with his officer to the foot of the iron ladder of the fire escape. When they were out of earshot Joe said quietly, ‘Very bold of you in the circumstances, I think, Sergeant, to volunteer for a climb like that?’

He paused, waiting for a response. Armitage looked truculently at his feet.

‘The leg, Bill? Anything you want to tell me about the leg?’

Armitage’s face stiffened with resentment. ‘Following me down the street last night, was it, sir?’

Joe was unapologetic. ‘Yes. Couldn’t help noticing you were favouring your left leg . . . when you thought no one was looking. War wound, I take it?’

‘It comes and goes, sir.’

‘For example it comes when you think you are unobserved and goes when you’re up for a medical?’ Joe enquired with an interested smile.

Armitage’s eyes glinted and his chin came up in defiance. ‘All right, so you can get me sacked for disability . . .’

‘And deception.’ Joe was not prepared to let this go. ‘I remember every recruit has to make a statement about his physical condition as well as prove it in the medical examination. And the three months’ training is no cakewalk. I’m surprised that you managed to pull the wool over so many eyes for so long, Armitage.’

‘So am I,’ he admitted. ‘And I can tell you it was bloody painful! But there were some good fellers who knew when to look the other way. Five years ago, the force was desperate for a certain calibre of recruit and in all other ways I fitted the bill. I’ve had no complaints. My record is a good one, you’ll find when you’ve time to check it. Perhaps you already have, sir?’

Joe was silent for a moment, wondering exactly what he had uncovered and what action he should take.

‘There’s a telephone in reception. One call should do it, Captain.’ The voice was icy and resigned.

The use of his old army rank was the only appeal the man would allow himself, though it was potent in itself, Joe recognized. He was too proud to allude to the many favours he’d done Joe over the months they’d fought together; it was bad form for survivors of the war to mention their experiences even to those who’d shared them. For men of his generation, four years of life – if you could call it that – were edited out of conversation. But not out of memory. Joe remembered the cups of weak tea proffered with a smile and an encouraging quip, the last drops of the sergeant’s rum ration swirling muddily in the bottom of his dixie. ‘Sippers? Naw! Go, on – finish it! You’re the barmy bugger who’s going over the wire. I’ll keep the next ration safe. Be here when you get back, sir.’

And the life-saving shot of raw spirit was, indeed, there waiting for him but much more. Still fifty yards short of the trench and a grey dawn breaking, he’d been spotted. Rifle bullets cracked around him as he wriggled on elbows and belly, following the intermittent shelter of a tuck in the land. A bullet through his shoulder, exhausted and drained of any will to go on, Captain Sandilands had slumped on to his face on the earth waiting for death.

‘Fucking sniper!’ Bill’s voice growled suddenly in his ear. ‘Overdone it this time, though! We got a flash of him when he started having a go. Lads have got him in their sights. Listen! That’ll make him keep his bloody head down – if it’s still on his shoulders! I think we could break for it now. You okay?’ And strong hands had hauled and pushed and rolled him the rest of the way back to shelter.

‘Perhaps I’m one of those fellers who know when to look the other way? It’s a skill I learned from a past master of the art in India,’ said Joe.

They watched in companionable silence as the constable swarmed fearlessly up the fire escape. ‘Tell me, Bill, did you ever stop counting those minutes?’ Joe asked quietly.

Armitage responded at once to the allusion. Perhaps it had been in his mind also. ‘Funny thing that. The counting had become so engrained I missed it when it all came to a stop. It kept me going. We all had to find our own ways of getting through.’

Joe was remembering the iron gleam in the sergeant’s eye as he fired a captured enemy machine gun at a row of German infantry emerging from their trench only yards away. They’d been sitting ducks for the raking gun. When, finally, the pitiless racket stopped and no more figures came on towards them through the smoke Joe had touched Armitage’s shoulder briefly with a stiff, ‘Well done, Sarge!’ He’d realized with a shock that Armitage had been counting throughout. ‘Twenty-five!’ he’d said with satisfaction. ‘Every bugger I get, I reckon as another minute off this bloody war. So that’s near half an hour saved, Captain!’

Joe had known many men go through the war without ever firing their rifle. Some, no more than boys, he’d seen close their eyes before firing. Some had loosed off everything they had at the horizon. But not Armitage. He had placed every shot deliberately and counted every hit.

Joe’s thoughts were interrupted by a triumphant crowing from Constable Sweetman who took time off from his climb to point to his left and stick a thumb in the air, indicating he’d spotted something of interest. He finished his climb, mimed jemmying and then smashing the window, and began the descent. This was done more slowly, with an eye open for evidence. When he reached a piece of roof invisible to those standing below he moved sideways from his course and, pausing, took a white handkerchief from his pocket. Using this, he carefully picked up an object and examined it uncertainly. Coming to a decision, he adjusted the handkerchief and took the thing firmly between his teeth before continuing his descent.

‘Good Lord, Sweetman!’ said Cottingham, impressed, handing back his helmet. ‘It only took you four and a half minutes to get up there. Well done! What athletic ability! Nothing like it since Douglas Fairbanks swarmed up the rigging in The Black Pirate.’

With a flourish, Sweetman removed the object he’d retrieved from between his clenched teeth and gingerly held it out. ‘’Cept this should be a dagger, sir, or a cutlass, maybe! Murder weapon! Would this be the murder weapon, sir? It’d rolled under a lead flashing. Hard to spot! But at least the rain’s not got at it. Look here, sir. And here. Them’s hairs . . . red ’uns. And that there’s not tomato ketchup neither.’

They all looked with curiosity at the fireside poker.

‘No, indeed,’ said Cottingham. ‘And, again, well spotted!’ He took a brown paper evidence envelope from his murder bag and wrapped it loosely around the poker. ‘I’ll get this straight down to the lab, sir. It may have prints on it.’