This is a fine example of media shortcomings during this. Pym is the BBC's Health editor, yet he tweets this out, gaining far more interaction than his messages usually do.
Basic maths says that the 7 day average increases if the daily figure 7 days ago is lower than the daily figure now. As this is deaths by day of reporting, not deaths by day of occurrence, the fact that it was bank holiday last week and therefore Tuesday’s number was artificially low, the rolling average was bound to increase slightly today. It does not mean (as this tweet implies) that the number of people dying every day has started to increase.
This is a misrepresentation of the facts, reported by someone who should know better and then even worse, retweeted by at least one MP.