"Grave matter" joke

This is a joke told by Dave Allen on one of his
shows (British program 'Dave Allen at Large').
A drunk leaves a bar and decides to take a shortcut through a
graveyard. It is raining heavily and very dark. The drunk
fails to see an open grave and falls into it. He tries to
climb out of it, but it is too deep and the rain has turned
the dirt to mud and has made it too slippery to climb. He
gives up after a while and decides to spend the night there.
A while later, another drunk leaves the same bar and decides
to take the same shortcut through the graveyard. He, too,
falls into that open grave and tries to climb out but the
mud is too slippery. The first drunk is still sitting there
and watches as the other drunk tries but fails to get out.
The first drunk stands up, taps the second drunk on the shoulder
and tells him, "You'll never get out!"
He did.
Dave Allen is an excellent storyteller and a very inventive
comedian. I'm afraid that just reading it here doesn't do justice
to it.