Unofficial motto 
"Non gratum anus rodentum"
("Not worth a rat's arse" or alternately "Couldn't Give a Rat's Arse")

Tunnel Rats

Oh, they had boundless courage, those small slight Engineers
As down in the Phuoc Tuy tunnels so dark and dank and drear,
With torch and sharpened bayonet and loaded pistol too
They made their lonely silent way to what they never knew,
There could be waiting enemy or booby trap en-trail
Or even deadly serpents tethered by the tail.

These thoughts were always in their minds as they made their lonely way
Wondering if they would again see the light of day,
The sweat runs down into the eyes, the earth close to the back
No place to think of other things when it’s Oh so still and black,
Don’t forget the spiders, the scorpions and the bats
Or the sword thrusts from the side and crafty punji traps. 

Oh, the fear came at times and claustrophobia too
But they put it from their minds as they had a job to do,
They were Aussie soldiers, no braver in the land
They carried on with the task without a big brass band,
Eventually their tours were up and they came back home
Happy with their families they had no wish to roam.

These quiet men, old Tunnel Rats, if you meet one in the street
You could not tell from looks alone they’re the bravest you could meet,
When young men, barely past their teens they faced their fears alone
You’ll likely find it very strange but most still roll their own,
They have one wish, when they should die, don’t bury them below
But spread their ashes in the sun where the grass and flowers grow.

(Alex Elliot)