Aurum Italicum or Lords and Ladies. It's a white lily and the berries turn red. It's pretty but best left alone as it's poisonous.

+1 for arum lily

Many thanks to you both!

There's a very attractive garden variety A.metallicum Marmoratum which has lovely variegated leaves. They appear in late Spring after the spring bulbs have more or less finished and disappear again by late midsummer. Mine is happy at the foot of a conifer hedge and in deep shade most of the time.