That is the seed head of an Arum, probably maculatum, but it could be A italicum. At some point you will have had green leaves or possibly variegated ones, followed by a strange shaped green flower with a purple spike in the centre.
The seeds are poisonous, but since they are so inedible to humans the chances of anyone eating enough to kill are very small.

Thank you Owdboggy, I have no idea how we got this - it's in our chicken run, but may have been there before we had our chicken run. It's a very interesting looking see head anyway!

Bird dropped seed? We get them all over the place from the roadside where they are plentiful. Not sure if Hens would eat them, but in any case they do not seem to kill the blackbirds etc. which DO eat the berries.