Bertie thought quickly. It was no use telling her that it was to lock her out; that would not have gone down well. ‘Security,’ he said quickly. ‘If a burglar climbed down the chimney, then he wouldn’t be able to steal my things.’

Irene raised an eyebrow. ‘Oh, I see. But it would be all right for him to steal my things, would it? Or Daddy’s? Or even little Ulysses’s things?’ She paused. ‘But not yours. What sort of attitude is that, Bertie?’

Bertie could see that he was being misconstrued – again. ‘But I didn’t mean that, Mummy!’ he protested. ‘You and Daddy have a lock on your door, so you could stop him taking your things.’

Irene gave Bertie a hug. He felt himself being enveloped; it was like drowning, he thought. ‘You shouldn’t want to lock Mummy out,’ she said. ‘Boys should have no secrets from their mummies, Bertie! A boy’s best friend is his mummy – not only when he’s a boy, like you, but for the rest of his life too.’

Bertie looked dismayed. Could this possibly be true? If it were, the future certainly looked bleak.

‘Of course, you can have other friends,’ conceded Irene. ‘Olive, for example. She’s a nice little girl, isn’t she? And you appear to be very friendly with her, don’t you?’

‘No,’ said Bertie. ‘I hate her, Mummy.’

‘No, you don’t,’ said Irene quickly. ‘Don’t talk such nonsense, Bertie, even as a joke. How can you hate Olive? She’s lively and engaging. She’s fun. No, you don’t hate her, Bertie.’

Bertie wanted to say: how do you know, Mummy? But he could not say that. In fact, he could say nothing, because anything he said would be immediately refuted by his mother, and it was no good arguing with her. She was like the weather – always there; and to resist her was like trying to resist the weather itself. There was just no point.

Now, trying to make out what was in this letter from Akela, he remembered something that he had read in that book he had borrowed from the library, 100 Things for a Boy to Do: Part 1. There had been a feature in that book called ‘Tips for Spies’, and it purported to be written by somebody called the Grand Spymaster, First Class.

‘If you need to read an intercepted letter,’ the article ran, ‘don’t slit the envelope open – the recipient will be very suspicious. Rather, wait until the letter is passed on to you to forward to another person. Then, making sure that you are not seen by the first person, you should gently steam open the flap. The contents photographed, the letter can then be re-sealed, and the information passed on to headquarters.’

Gently steam open the flap. Well, Bertie had no steam in the room, but he did have his breath, which was, he believed, warm and moist.