What is/was the Liberty Hall that's referred to both in episodes of Downton Abbey and in Christie's "The Body in the Library?"

Liberty Hall, a term for a place where one is free to do as one wishes. The origin is probably Oliver Goldsmith's play 'She Stoops to Conquer' (1773), where in Act II Hardcastle says "Mr. Marlow - Mr. Hastings - gentlemen - pray be under no constraint in this house. This is Liberty-hall, gentlemen. You may do just as you please here."