Cemented box with a black cable sticking out, buried in the back garden

WIAWSNB

Mumili said:

Ectophile said:

WIAWSNB said:

Could you scrape out the inside, please, and also give it all a good wash?
Can you determine the material? Try scraping it with a knife or file. If you tap it with a hammer, is it metallic or plastic - does it go boing or does it clunk? If you hit it quite hard, does it dent?

And if we never hear anything again from the OP, then we will know it was live!

Can confirm that OP is alive. 
Turns out it was indeed a large washing line base. Thanks for the help — much appreciated.

That area is sloping towards the house, and I need to flatten that bit to create a step. I tried to chisel and hammer it, but it's very sturdy.  Looks like someone in the ’90s poured cement and gravel into that hole like there was no tomorrow. 

I am thinking of digging it even deeper and burying it. It will probably affect the lawn quality in that area, but alas.

Please you survived :-)
How can you dig it deeper? If you are going anywhere near that level of work, you might as well remove it. But, I bet it's heavy!
If you don't fancy getting an SDS drill, then a cold chisel and club hammer will do it. With goggles...
Set the chisel on the concrete, somewhere in a radiating line from the pole, and thump away. Hit it forcefully, but don't exhaust yourself - the idea is to keep on impacting in the same place for a good few minutes - very good chance that stress fractures will start to form, until - ideally - you split the lump. 
Or, you may need to knock chunks off it...

Glad

Lump hammer and a big chisel?

Robin9

@Mumili  Now that you've found your washing line base could you find mine please -  lost Autumn 2023 !

Eldi_Dos

Mumili said:

Ectophile said:

WIAWSNB said:

Could you scrape out the inside, please, and also give it all a good wash?
Can you determine the material? Try scraping it with a knife or file. If you tap it with a hammer, is it metallic or plastic - does it go boing or does it clunk? If you hit it quite hard, does it dent?

And if we never hear anything again from the OP, then we will know it was live!

 Looks like someone in the ’90s poured cement and gravel into that hole like there was no tomorrow. 

I am thinking of digging it even deeper and burying it. It will probably affect the lawn quality in that area, but alas. 

Before 1995 cement used to be sold in bigger bags than the now standard 25 kilo, so there was a tendency just to use the whole of the large bag rather than cart it away or dispose of it somehow.

As regards digging it up,that is what I would do, dig around it then using some levers flip it over, then dig hole deeper so it will not effect new lawn,flip concrete back into deeper hole and backfill, a lot less labour intensive than other methods.