Please can anyone help me identify this weed

[Anotherunimaginativeusername]

It grows to about 4 feet high and has black berries at the end of the summer, roots go really deep and I'm not able to dig it out. I've found some really thick sideways travelling roots today as well which probably explains it popping up everywhere. Seems really invasive and has infiltrated my garden via a plot of council-owned amenity land which borders our garden.
Any help to identify it and tips to get rid much appreciated.

Danewort?

Also known as Dwarf Elderberry.

Yes this it definitely it, thank you.
Will keep on digging it up but think we are fighting a losing battle with it coming in from neighbouring land.

Does seem pretty tough to eliminate, there's a few tips on how to stop it, but as you say, if its coming from a neighbouring property you may have some trouble.

Perhaps contact the company that owns it and see if they will do anything about it, it's worth asking.

Good luck