If you could imagine a David Chipperfield Architects’ Christmas lunch, what venue would you pick? Some minimalist number in Camden? Possibly Moro in Clerkenwell? The list would be very long before one got to Sweetings, which is where it is taking place this year. One of the most traditional restaurants in the city of London, it’s all stuffed shirts, old school ties, oysters, Guinness and heavy English puddings. Not exactly a Chippo kind of place, you wouldn’t have thought – more a kind of Robert Adam or Quinlan Terry hang-out really. The only remaining question is why? Answers on a postcard please. The world of architecture needs to know.