  Based on a recent proposal for the gravitational entropy of free
gravitational fields, we investigate the thermodynamic properties of black hole
formation through gravitational collapse in the framework of the semitetrad
1+1+2 covariant formalism. In the simplest case of an Oppenheimer-Snyder-Datt
collapse we prove that the change in gravitational entropy outside a collapsing
body is related to the variation of the surface area of the body itself, even
before the formation of horizons. As a result, we are able to relate the
Bekenstein-Hawking entropy of the black hole endstate to the variation of the
vacuum gravitational entropy outside the collapsing body.
