A real suckerer: see https://majura.org/woody-weeds-follow-up-working-party-19032017/. I haven't been along the gully that runs parallel to Valour park for a while. There were hundreds! between the fence and gully and down into the gully, all suckers from the Valour park plantings. We had a couple of older trees south of the gully in the corner of Valour park. I now find the the occasional regrowth; may be there are still bits of roots in the soil that don't give up...
See discussion at https://hortflora.rbg.vic.gov.au/taxon/ad8d59ee-5340-11e7-b82b-005056b0018f and at https://hortflora.rbg.vic.gov.au/taxon/ad8d51d8-5340-11e7-b82b-005056b0018f