Without giving too much away and outing myself.. has anyone any ideas whether they have an answer to the following:

Employee currently homeless and living in their small work van. Some nights they're staying awake! Obviously this is going to harm their mental and physical health. Works take on it is it's outside work hours no duty of care etc.. 

Does anyone know different?

Thanks Sammy 

No idea what you do about it.

I did once discover that someone was sleeping in one of our conference rooms (girlfriend kicked him out, he couldn't figure out anywhere else to go), but that was long enough ago that I had someone else to report to, so I did and don't know what happened next (though he stopped sleeping in the conference room).

Do you have fatigue management policies this will affect?  Otherwise it feels like something to get HR on rather than H&S.

Is their employment tied to a licence? If they are caught over the limit it does not matter if the keys are out of the ignition and they are asleep in the back they would still be considered to be "in charge" of the vehicle.

Unfortunately I would say it is works problem as a reputation damager - don't appear to pay enough for housing and don't care the employee is living in (I presume) a liveried vehicle with the companies details on show.

You may also have insurance issues with the permitted use of a company vehicle outside of works hours.