You're mad.
2 seconds sound clip from The Hitchhiker's Guide to the Galaxy (1981) - Episode 3 sitcom.
You can hear this line at 00:20:36.344 in the Blu-ray version of the TV Series.
Quote context
[...]
- Hey, look at this! Any idea what these strange symbols on the walls are?
- Yeah. I think they're strange symbols of some kind. It's hard to tell with my shades on.
- I wish I had heads like you, Zaphod. I could have endless fun bashing them against walls.
- Yeah.
- Yeah?
- Yeah.
- These are the greatest shades in the known sky. Just take a look at the copy.
- I thought I just saw a movement down at the end of the corridor.
- There's no-one here. Trust me.
- Old mate, I trust you about as far as I could comfortably spit out a rat.
[...]