Ah-HA!!! For some reason when I first saw - in a Christmas story set in England - the word "panto" I thought it was a children's pantomime.
Last night, clarification of the term came in a Public Television program about the old days of vaudeville in USA. Panto in England is the same as the old vaudeville shows in US ! In fact, much of vaudeville's traditions were taken from the English panto. The program had some wonderful clips of really great old time performers in both US and English Music Halls - I recommend the hour to anyone with an interest in theater - if and when it shows up on your local PBS station.
Now, I did do a search for "panto" but so much stuff came up I just didn't have the heart to plow through all of the panto-listings sooooo, this is for general info and the two or three people out of the thousands registered who may have (fleetingly) wondered.