One of these

Cut down (twice) by neighbours as it was getting rather out of hand. Not sure if it started out in their garden, of ours, as it's pushed the fence panels apart and had grown into both properties.
I put killing stuff (can't remember what) into the stump, but it's sprouting into the lawn.
Original growing spot was behind my wellies.
And, yes, I know the fence needs a coat of summat!

It's popping up a good 6 or 7 yards away, now, with a solid lump under the new growth.
Any suggestions or solutions from the CC Massive?