Back then one of the big social events - masquerade catagory - was an annual *servants* ball in London. It was supposed to be just for the 'under the stairs' sorts - but it got popular and so lots of other folks tried to score tickets. Jeeves would qualify to buy tickets - and he *might* be persuaded to bring Bertie along.

It also had something of a 'gay' reputation. (In the modern sense of the word.)