How to determine the Host a VM runs on, if VM is 2012

Morning all

HyperV host on Win2012 (standard, not R2), guest is the same.

Time was, you could query HKLM\SOFTWARE\Microsoft\Virtual Machine\Guest\Parameters\PhysicalHostName on a VM to find out the name of the host it was running on, and this is handy for us as we run various scripts to update inventories and such. With a 2012 guest, sometimes that key is no longer populated and for the life of me I can't work out why. The Parameters key is there, but totally empty.

Any thoughts? As you'll know, W2012 has the HyperV integration stuff built in, so it's not like they're out of date or anything. One working and one not-working are both at the same patch levels.

Thanks

A