“I am fully acquainted with Dr. Ishiwaka’s theories.”

“Then you know it’s bollocks. All I did was say so in my essay, and Beeson gave me a failing mark! It’s totally unfair. I mean, Ishiwaka says these ridiculous things, like slippage isn’t to stop historians from going to times and places where they’ll affect events at all. He says it’s a symptom that something’s wrong, like a fever in a patient with an infection, and that the amount of slippage will grow larger as the infection gets worse, but we won’t be able to see that either, because it’s exponential or something, so there’s no proof of any of this, but we should still stop sending historians because by the time we do have proof, it’ll be too late and there won’t be any time travel. It’s total rubbish!” Mr. Dunworthy was frowning. “Well, don’t you think it is?”

Dunworthy didn’t answer.

“Well, don’t you?” Colin asked, and when he still stood there, “You can’t mean you believe his theory? Mr. Dunworthy?”

“What? No. As you say, Dr. Ishiwaka hasn’t been able to produce convincing proof of his ideas. On the other hand, he raises some troubling questions that require investigation, not a dismissal as ‘total rubbish.’ But you obviously didn’t come up here to debate time travel theories with me. Or to, as you put it, see what I was up to.” He looked shrewdly at Colin. “Why did you come?”

Here was where it got tricky. “Because I’m wasting my time studying maths and Latin. I want to be studying history, and not dry-as-dust books-the real thing. I want to go on assignment. And don’t say I’m too young. I was twelve when we went to the Black Death. And Jack Cargreaves was seventeen when he went to Mars.”

“And Lady Jane Grey was seventeen when she was beheaded,” Mr. Dunworthy said, “and being an historian is even more dangerous than being a pretender to the throne. There are all sorts of risks involved, which is why historians-”

“-have to be third-year students and at least twenty years old before they can go to the past,” Colin recited. “I know all that. But I’ve already been to the past. To a ten. It can’t get more dangerous than that. And there are all sorts of assignments where someone my age-”