De Vries was adamant the group should be highly disciplined. Its members were to keep a low profile, lead their lives as normal and do nothing to draw attention to them. They all adhered to this, apart from one member: a retired schoolteacher called Johannes, who cycled round the city in the same shabby suit whatever the weather. Johannes had a neighbour, a man who openly collaborated with the occupiers and was widely believed to have betrayed a Jewish family hiding in the town. For over a year Johannes had developed a seething hatred of this man but was powerless to do anything about it. Now the group was becoming active once more, he saw his opportunity.

De Vries was unaware of this. In fact he was so satisfied with the group that he sent a message to London informing the SOE that they were ready to move on to the next stage of their operation.

Two important railway lines passed through Enschede: one to the west that led to Amsterdam, Rotterdam and The Hague, and a separate line going east into Germany, both lines vital to the German war effort. De Vries’s instructions were to blow up both lines simultaneously.

The RAF dropped a consignment of weapons and explosives in Overijssel, to the north of Enschede, and de Vries started to prepare the team. The arms drop had included a dozen handguns – Spanish Llama pistols – and he gave one to each member of the group.

The night before the planned sabotage, disaster struck. As far as de Vries could gather, Johannes had gone round to the collaborator’s house and shot him with the pistol he’d just been given. The collaborator’s wife had managed to raise the alarm, and Johannes was arrested. It didn’t take the local Gestapo very long to break him, and within hours of the shooting they’d begun to round up other members of the group. One person they failed to find, however, was Frieda Mooren. She’d managed to slip out the back of her house and had gone straight round to where de Vries was living. They left immediately and went to the farm just outside Enschede where they’d stored the explosives.

The word from the city was that the hunt for the two of them was gathering pace: extra troops had been drafted in, along with a senior Gestapo officer from Amsterdam. They decided to attempt to blow up the railway line heading west. After that, they’d go north, to Amsterdam.

Because of the concentration of troops searching for them in the area, de Vries decided to sabotage the railway line further away from Enschede, close to Tusveld, north-west of the city. The farmer drove them to the area one morning on his way to market, stopping outside a small wood for the two of them to climb out of the back of his truck. They hid in the trees until the very early hours of the morning, when darkness wrapped itself around the countryside and not a sound was to be heard. De Vries whispered to Frieda that it was time to move, and began to crawl out of the undergrowth where they were hiding. She placed a hand on his back to stop him.