Taken at face value, there are some significant questions.
1. Everyone working close to him had been or was ill. Why did he not self-isolate?
2. 27/3 Wife fell ill. Why did he go back to work rather than self-isolate?
3. 27/3 Why was his house a target on 27/3 but not before?

4. When did PM first know?
5. If his house was a target on 27/3 and Durham was the safest place for his wife and child, why bring them back in April? What had changed?

6. If he was not sure whether he was fit to drive, he was not confident he had recovered. Why didn't he continue to self-isolate?
7. If he felt "sick" on the trip to Barnard Castle, he was still experiencing symptoms. Why didn't he resume self-isolation?