“They always have the same hours,” I said, “four to eleven.”

“Four to what?” he asked, looking up.

“To eleven,” I repeated sharply; “but you’d much better call round about three.”

He looked bewildered.

“Don’t interrupt,” I said, seeing him open his lips, “or I shall lose the thread. It’s rather complicated. You call at three by the little door in Whitehall on the Embankment side towards the Horse Guards looking south, and don’t ring the bell.”

“Why not?” he asked. I thought for the moment he might begin to cry.

“Oh, well,” I said testily, “you mustn’t ask those questions. All these institutions are very old institutions with habits and prejudices of their own. You mustn’t ring the bell, that’s all; they don’t like it; you must just wait until they open; and then, if you take my advice, don’t write a note or ask to interview the First Analyist. Don’t do any of the usual things, but just fill up one of the regular Treasury forms and state that you have come with regard to the Perception and Mensuration advertisements.”

His face was pained and wrinkled as he heard me, but he said, “I beg your pardon ... but shall I have it all explained to me at the office?”

“Certainly not!” I said, aghast; “it’s just because you might have so much difficulty there that I’m explaining everything to you.”

“Yes, I know,” he said doubtfully; “thank you.”