Eighteen!
2 seconds sound clip from the A Tale of Two Cities (1938) classic radio drama series episode.
You can hear this line at 00:52:31.059 in the radio play.
Quote context
[...]
(GUILLOTINE BLADE DROPS THUMP! OF HEAD CUT OFF)
(CROWD CHEERS THEN FALLS SILENT)
- Huh? Oh, true. I forget... what were you accused for?
- Who would think of plotting with a poor little weak creature like me?
[...]