What was the first novel ever written on a word processor?

Would best-selling novelist Len Deighton care to take a walk? It was 1968, and the IBM technician who serviced Deighton’s typewriters had just heard from Deighton’s personal assistant, Ms. Ellenor Handley, that she had been retyping chapter drafts for his book in progress dozens of times over. IBM had a machine that could help, the technician mentioned. They were being used in the new ultramodern Shell Centre on the south bank of the Thames, not far from his Merrick Square home.