Anybody seen one of these before?

Been out walking and foraging today and came across a whole load of these.  They were actually grown behind a fence, but whoever planted them wasn't that bothered about them as they were scattered all over the ground.  One had fallen on the other side of the fence and intrigue I picked it up.  I'm assuming it's edible, but haven't cut it open yet, wanting some idea what to expect, sweet, savoury...?

I couldn't work out whether they had come of those climbing vine-type plants or a low tree.  There was one still hanging in the tree, but it may have been a vine climbing up that tree.  it's extremely prickly and you can see the size on the photo.  There's no discernable smell from the outside.  Anyone of you clever people out there...?  If no-one comes up with anything I'll cut it open tomorrow and show you the insides too.