Beautiful Sainte-Agnès in the South of France - and its spectacular underground fort of the Maginot Line - feature in The Major Minor Murders

The underground fort of the Maginot Line is a remarkably well-preserved maze of corridors and gun emplacements overlooking the France-Italy border

Extract from The Major Minor Murders...

The final ascent brought them to a small parking area. Maurice reversed the car to a low wall and they all got out. The cold air hit Barney like a slap in the face. Then the view kicked him where it hurt. ‘Whoa… Keep back from the wall, Ffiona.’

Far below them lay the busy motorway perched on stilts, the sprawling town of Menton and the sea beyond.

It was the first time he’d heard Maurice laugh. ‘The views are even better up there.’ He was pointing up to the left, where the cantilevered deck of a restaurant jutted impossibly out over the sheer drop.

Barney retreated another couple of yards, just to be on the safe side. ‘Very funny. Thankfully we’re probably heading under the ground, not over it.’

Maurice smiled and gave them his phone number, saying he’d wait in the restaurant for them. They must call if they needed him, he said.

They walked towards the village centre and found the main entrance to the underground fort. The notice on the daunting concrete-faced entrance confirmed that the museum and complex were closed. The weighty chain and padlock seemed to tell bored youth: don’t even think about it.

‘Oh well,’ said Barney, ‘looks like we might be better doing what Jenny suggested and start asking around the local bars.’

But Ffiona was having none of it. ‘No,’ she said. ‘There must be another way in.’ As if about to prove her point, she turned to walk back the way they’d come. ‘I’m sure I saw a path running around the hill below that wall.’

To Barney’s chagrin, she turned out to be right. People without vertigo never understood it but following Ffiona down on to the path, inches from a sheer drop onto rocks, his whole body was going rigid. He steeled himself to make each single step, hugging the hillside on his left as they made their way round.

After a lifetime of steps he finally caught up with Ffiona. She was standing below a grouping of enormous, round-topped bunkers thrusting their way out of the rock. He was panting, leaning with both hands on the heavily-weathered concrete, his back to the drop.

When he dared look up, he saw her reaching into a slit in the wall. He focused on the concrete inches away from his face.

She knew of his phobia and tried to sound encouraging. ‘It’s OK, Barney. We can get in here, no bother.’

All he could say was: ‘Aye, maybe it’s no bother for you.’ Sometimes her never-say-die attitude was a pain in the backside but he knew he had to follow, one careful, pebbly step after the other until he saw her hands reaching out to him from the darkness inside. Tense or not, he registered that he had just stepped over some splintered wood. It looked like someone else had been here before them and hadn’t thought twice about smashing the opening’s feeble old shutters. Then he was in, standing next to her, the worst behind him. He’d never been happier to be in complete darkness in an underground labyrinth almost two hundred feet deep...