'What you want, old man,' I said, 'is a policeman's helmet.'

'Do I, Bertie?'

'If I were you, I'd just step straight across the street and get that one over there.'

'But there's a policeman inside it. You can see him distinctly.'

'What does that matter?' I said. I simply couldn't follow his reasoning.

Sippy stood for a moment in thought.

'I believe you're absolutely right,' he said at last. 'Funny I never thought of it before. You really recommend me to get that helmet?'

'I do, indeed.'

'Then I will,' said Sippy, brightening up in the most remarkable manner.