Earthman, we are now deep in the heart of Magrathea.

3 seconds sound clip from The Hitchhiker's Guide to the Galaxy (1981) - Episode 3 sitcom.

You can hear this line at 00:28:03.853 in the Blu-ray version of the TV Series.

Quote context

[...]

- So they eventually gave up and left the Earth by their own means, shortly before the Vogans arrived.

- The last ever dolphin message was misinterpreted as a surprisingly sophisticated attempt to do a double-backwards somersault through a hoop whilst whistling the Star Spangled Banner, but in fact the message was: 'So long, and thanks for all the fish.'

- In fact, there was only one species on the planet more intelligent than dolphins.

- And they spent a lot of their time in behavioural research laboratories conducting frighteningly elegant and subtle experiments on man.

- The fact that man once again completely misinterpreted this relationship was entirely according to these creatures' plans, as Arthur Dent will shortly discover.

- Earthman, we are now deep in the heart of Magrathea.

- How do you know I'm an Earthman?

- These things will become clear to you. At least clearer than at the moment.

- Oh. I think I should warn you that the chamber we are about to pass into does not literally exist within our planet.

- It is simply the gateway to a vast tract of hyperspace.

[...]