Based on historical facts, this emotional Sainsbury's advertisement remember us the unofficial Truce that German, Scottish and French platoons did during the 1914 Christmas.
During several days, soldiers both sides stopped fighting and enjoyed the seasonal good feelings together (they played football, exchanged gifts, etc.). The militar leadership, obviously, did not like the news when they knew it and all the soldiers where moved to other fronts and punished for "fraternizing with the enemy". Not to said, having another Christmas truce in 1915 was totally unthinkable...
There is also a film about this event, directed by Christian Carion in 2005.
Enjoy it and... Merry Christmas to you all, students!