that the earliest sunset happens approximately December 8th and latest sunrise approximately January 5th - set around the shortest day of approximately December 21st.
this matches with what I was observing (albeit made much more difficult by variable weather conditions!) that it was still getting darker in the mornings but might be getting just a tiny bit lighter in the afternoon-evenings.
not sure whether BBC2 is being ironic/sarcastic but they've scheduled the classic "Summer Holiday" musical film for this afternoon (up against xmas tat on C4 & C5) as we head deeper into winter.