Three teams in Championship history have been top of the table on Christmas Day but found themselves in the play-offs having missed out on automatic promotion. Each time this happened, all three failed to be promoted.
Ipswich Town were top in 2004-05 with 49 points, but ended up finishing down in sixth and then losing in the semi-finals to West Ham.
Watford were top in 2007-08 with 43 points but also ended up in sixth – and also ended up losing in the semi-finals, this time to eventual winners Hull.
Most recently, Leeds were top in 2018-19 with 48 points, before finishing third but then losing at the semi-final stage to Derby.
What does that all mean for this season? Sheffield United were top last Christmas before dropping out of the top two – but, after thrashing Bristol City last week, do at least look set to reach the final.