Mr. Herriot refers to the period of Tricki's hospitalisation as a "happy period" for himself and his partners. During this fortnight, Mrs. Pumphrey kept sending eggs, wine, and other luxuries meant for Tricki's recovery. However, since Tricki needed no special food — only a strict diet and exercise — the staff enjoyed all these delicacies themselves. Thus, the partners ate and drank well, making it a thoroughly enjoyable time for them.
Source: A Triumph of Surgery, Chapter 1
The question asks you to explain the "happy period," so you must mention the reason — Mrs. Pumphrey's luxury food meant for Tricki was consumed by Mr. Herriot and his partners. Examiners expect this specific detail. Avoid vague answers; be precise about what made it "happy."