The MC at the Bath Assembly Rooms was Mr King- a historical personality renowned for his rules and regs, and his ability to keep drunken louts under control, bring shy maidens to the attention of young men wihout a partner, and get dowagers their Sedan Chairs when they wished to leave. Mr King was paid fo rhis work- but he was yet considered a gentleman.

In P&P, or at least in P&P2, it does seem to me that the MC is Sir William Lucas. Or at least that Sir William thinks he should be the MC.