Cork filling for an R-class battleship

How tough would an R-class battleship be if filled with cork for anti-invasion service?

A substantial amount of cork could be fitted and would affect torpedo damage, but no estimate of the protection is given.

An R-class battleship could accommodate substantial cork filling for the imagined anti-invasion role. Cork is considered capable of affecting the consequences of torpedo attack, but the scale of that effect remains open. No detailed arrangement or calculation establishes how much tougher the ship would be.