The mystery of the Acacia longifolia in my yard continues

I have written something about this plant, previously, although it is not apparent from the title.
My Bad!
http://peonyden.blogspot.com.au/2011/08/daffodils-tete-tete-in-flower-early-and.html
This year it is flowering even more early in the season.

Flowers starting to open yesterday 8 July 2014

Flowers of Acacia longifolia

Thing is, this plant occurs below Robertson, on the Sandstone Plateau. But it does not occur naturally up here on the basalt soil. I know I did not plant this plant here. In fact, I was tempted to remove it, but decided to leave it to grow, when I first recognised that it was not a Blackwood Wattle (which is completely normal here). I decided to let it grow, to see what species it is. Now that I know, do I let it grow on?

Flowers of Acacia longifolia.
This is one of the Acacias with flowers on "rods"
not in a ball-like structure.

It is now taller than the adjacent Blackwood self-planted seedling. It will probably grow quickly, and then die off. I hope so. Whereas Blackwoods are huge trees, and they live a long time. Landscape trees.
But I do not want two huge trees growing side by side, directly in front of my house. They will cut off the natural light in the house.

"Leaf " (phyllode) of Acacia longifolia
Note veins and short stem (pulvinus)
and location of the "gland"
close to the stem. (top right)

Pulvinus (stem) of the "phyllode"
(swollen stem which acts as a leaf)
Note the gland on lower edge of phyllode
and the slight change in angle of the edge of the phyllode.
Most of the Wattles with phyllodes have these glands.
The theory is that they are there to attract ants
which in turn would protect the Wattle from insects.
Possibly a remnant (archaic) structure.

Two main veins running more or less parallel,
Several minor veins also apparent.

In this photo, the two dominant veins are clearly evident.