Just as he succeeded in doing this, lights from a vehicle parked in the drive in front of a nearby house flooded the area, and two police officers stepped out of places of concealment in nearby gardens.

For a moment everyone froze, then Raff and Sevvy turned to run, but were caught and though they struggled desperately they were quickly handcuffed.

Dorling made no attempt to run and when the police had captured the two youths, he thanked them profusely for saving him from the muggers.

‘We aren’t muggers,’ Raff said. ‘We did a job for him and he wasn’t going to pay us what we agreed. I’ll tell you all about it if you’ll take it into consideration.’

‘He’s lying!’ Dorling exclaimed. ‘You can’t believe the word of a thief against mine.’

‘Oh, but we do. We’ve been keeping watch on you for a while, Mr Dorling, and are already aware that you’ve been involved in certain dubious incidents. Good thing we were following you tonight, eh?’

‘But I’m not involved in anything dubious!’

‘Our various witnesses say differently, and the lads’ evidence will be very helpful. We’ll find out more about this at the station, shall we, sir? And since you came here on foot, allow us to give you a lift there.’

The following day around midday, after negotiations at senior levels had been concluded, the fire and rescue service sent a team to help the three heritage officers explore the tunnels.

Angus and Nell were allowed to watch from a safe distance and the word must have got out somehow, because a few other spectators turned up.

‘Oh, hang it,’ Angus exclaimed. ‘Let’s invite Adam and as many of the others as are free to come and watch.’

It wasn’t the most riveting show, because there was a lot of peering into the tunnel and slow arrangements of apparatus. But at last, when the tunnel had been deemed safe, the heritage officers were allowed into it.

They came out beaming and Angus hurried across to them before anyone could stop him. ‘Well? Don’t keep us in suspense.’

‘The passage forks into two. One branch goes through to the biggest house at the inner end of Saffron Lane. Most ingenious to have two escape routes. The other part of the tunnel has caved in at one stage, but it won’t cost a lot to shore it up and make it safe, then we’ll find out where it leads – my guess is that little park just along the street, the one where there’s an electrical substation. I’ve seen communication centres linked into places like that before.’

He beamed at them. ‘We’re bound to get funding for that, because it won’t cost much and it’s quite an important find.’

‘Good heavens. And all this was unknown till we discovered that room?’

‘Absolutely. Places are still coming to light here and there across the country, even all these years after the end of the war. There were groups of people who thought ahead during the war, especially in the early years, when they were expecting Germany to invade at any moment. They wanted to be ready to go into resistance mode.’