frankv:

 

The underground part of a solar garden light.

 

 

 

Yep I have a few of those

elpenguino:

 

Looks like the bottom of a plastic solar powered garden light, although its hard to see exactly if the top of it is designed to socket into a piece of pipe.

 

 

 

My solar lights have the bit in this post, that the tubular bit sticks into and the light sticks into the top of that

steve2222:

 

Was it near a boundry?

 

It was, although the yard is 4.5m x 5m so it's all near a boundary :)

I've had another look at the old photos I mentioned (the real estate agent used a mixture of old pictures on the listing 🙄) and I can see that one of the lights was right about where I found this stake. I need to give my dirt patch a thorough raking anyway, so I'll hopefully uncover any more light stakes that have been left behind.

Thanks all for your suggestions.

     >Ancient plastic arrow head. Call a museum!<

From the Plastocene Era?