can polarizing filters work as ND filters?

[Sloane]

A polarizer polarises directional light. Like the sun's. It also absorbs up to 2,5 stops of light.
If the main light is not directional (overcast day, open shadow, etc.) it will not (cannot) be polarised by the CP. But it will still be absorbed, and thus the CP will act as an ND filter would.
There is however nothing 'graduated' about it.

 

[Garbz]

But Steph a polarisers on a cloudy day may not be visibly different from an ND filter. Naturally the polariser makes a difference to polarised light, but it still has a neutral density component to it.