Sibbie couldn’t believe how well it all went, and how easily they got to speak to Mr Brown. One of the policemen believed them and knocked heavily on the door that Sibbie and Marjie thought led to the flat upstairs. Without waiting for a reply, the policeman opened the door and shouted, ‘Is there a Ted Brown there? Are you unharmed?’

A man came down the stairs. The girls looked at each other, as he didn’t fit the scant description they’d had. But Marjie wasn’t going to be put off. ‘Where’s Ted?’ And then, with a stroke of genius, she used the code-words they had been given: ‘fallen apples’. ‘Ted, are you up there? My mum has told me to call in and tell you that she has some fallen apples for you.’

Sibbie felt like jumping for joy when a voice called out, ‘Yes, I’ll be down in a minute.’

They’d done it! The feeling she had, Sibbie knew Marjie had too, as her face beamed.

‘Ted’ came down the stairs, smiling. He nodded at them both, but didn’t speak. The other man pulled out a card and showed it to the policeman as he ushered him towards the front door and went outside with him.

When he came back in, he was alone. ‘I explained to the police what was going on and who you were, and that they had no need to look for anyone else in connection with a burglary. Well done, girls. You will do your country proud. I’m Captain David Howkins, by the way.’

Both girls stood to attention and saluted.

‘Stand at ease. Now, what are your names?’

‘I’m Sibilia Charvet, sir.’ Sibbie had chosen to use Montel’s surname as her cover name, and she’d been told to use a similar name to her forename, so that Marjie didn’t get mixed up and could still call her ‘Sibbie’. Marjie had chosen Margarita, for the same reason, and her surname because it rhymed with Hérault, where she was born, and would be easy for her to remember. ‘And this is Margarita Barrault.’

‘Excellent. I really hoped that you wouldn’t break your cover and fail at the last hurdle. Look, I’ll get clearance from your commanding officer – you can listen in, if you like, so that you are sure – but we would really love to take you to dinner. You can’t have had any fun since being dumped here. Where have you been staying?’

Sibbie felt unsure, and she could see Marjie did, too.

‘Ha! You two are tip-top. Come, let’s talk to your commanding officer and then we’ll report to Baker Street and let them know how you passed with flying colours. Then you can relax and not feel as though we are trying to trick you.’