When Margaret comes to visit the new baby, Elizabeth shares that they considered naming him George or Louis but decided on Andrew. George and Louis are the real life names of Prince William's sons, although Prince Louis was not yet born when this episode aired.
This episode takes place in 1959 and 1960. The wedding took place on May 6, 1960.
Before and during the birth and racket ball match scene (around minute 45) we can hear the Mozart soprano and choir piece "Laudate Dominum," KV339.
Both Matthew Goode (Tony) and Anna Chancellor (Lady Rosse/Tony's mom) appeared in Downton Abbey (2010), though in separate seasons. Matthew Goode played Henry Talbot. Anna Chancellor played Lady Anstruther.