"In space travel, you see," said Slartibartfast, as he fiddled with some instruments in the Room of Informational Illusions, "in space travel ..."
He stopped and looked about him.
The Room of Informational Illusions was a welcome relief after the visual monstrosities of the central computational area. There was nothing in it. No information, no illusions, just themselves, white walls and a few small instruments which looked as if they were meant to plug into something which Slartibartfast couldn't find.
"Yes?" urged Arthur. He had picked up Slartibartfast's sense of urgency but didn't know what to do with it.
"Yes what?" said the old man.
"You were saying?"
Slartibartfast looked at him sharply.
"The numbers," he said, "are awful." He resumed his search.
Arthur nodded wisely to himself. After a while he realized that this wasn't getting him anywhere and decided that he would say "what?" after all.
"In space travel," repeated Slartibartfast, "all the numbers are awful."
Arthur nodded again and looked round to Ford for help, but Ford was practising being sullen and getting quite good at it.
"I was only," said Slartibartfast with a sigh, "trying to save you the trouble of asking me why all the ship's computations were being done on a waiter's bill pad."
"Why," he said, "were all the ship's computations being done on a wait-"
Slartibartfast said, "Because in space travel all the numbers are awful."
He could tell that he wasn't getting his point across.
"Listen," he said. "On a waiter's bill pad numbers dance. You must have encountered the phenomenon."
"On a waiter's bill pad," said Slartibartfast, "reality and unreality collide on such a fundamental level that each becomes the other and anything is possible, within certain parameters."
"It's impossible to say," said Slartibartfast. "That's one of them. Strange but true. At least, I think it's strange," he added, "and I'm assured that it's true."
At that moment he located the slot in the wall for which he had been searching, and clicked the instrument he was holding into it.
"Do not be alarmed," he said, and then suddenly darted an alarmed look at himself, and lunged back, "it's ..."
They didn't hear what he said, because at that moment the ship winked out of existence around them and a starbattle-ship the size of a small Midlands industrial city plunged out of the sundered night towards them, star lasers ablaze.
They gaped, pop-eyed, and were unable to scream.