I believe that you are correct...
... long ago when most of the world was a part of Greater Britain, decent crockery was expensive. To cushion your questionable quality crocks from the shock of the hot tea you would therefore put the milk in first.

In the "best houses" you would therefore see scolding tea poured directly into the cups, with the milk to follow, just to show that you had money to buy the very best china. It is widely recognised that tea made that way is horrible but no matter - it's the showing off that counts. See also fashion.
( Ugi , it's a game of give and cake, Thu 10 Mar 2011, 11:43, Reply)