Are you sitting comfortably?

 
Anyone of 'a certain age' in the UK will be very familiar with the
catchphrase "Are you sitting comfortably? Then I'll begin."

This was always the introductory line of the radio programnme 'Listen with Mother' which was obligatory pre-school listening for my age group. The programme began in 1950 and carried on until 1982. It seems the origin of the question is uncertain as both Julia Lang (the original presenter) and Frieda Fordham (a psychologist who advised the BBC) have been credited with it.

All know is that if you say 'Are you sitting comfortably?' to any of my contemporaries they will automatically add the 'Then I'll begin..."