Where is my ticket

An old scientist, whom everybody in England knows very well, is travelling by train. When the ticket-inspector comes to the scientist and asks him for his ticket, the old man begins to look for it in his pockets, in his bag and suitcase, but cannot find it.
"There is no hurry", says the ticket-inspector, who knows the scientist very well. "I can come again at the next station." But at the next station it just the same. The old scientist cannot find his ticket.
"That's all right," says the ticket-inspector."That's all right."
"Oh, but I must find the ticket," says the man. "I want to know where I am going."