The stabbing story seems reasonably unusual for the reasons that others have given – plus there isn’t much other news around. I notice it’s been knocked out of the top 3 stories on the BBC website now, though.
BBC doesn’t tend to self-generate a lot of stories, particularly over the Christmas/New Year period when staffing is pretty light. There’s no parliamentary business, very little court reporting (I notice Stephen Lawrence trial is up and running again today, though), and very little business news.
Like it or not, day-to-day news is driven by political activity and the timed release of reports and statistics, and that dries up over the Christmas break. Leaving you with crime and dead celebs.