Further to this, I am starting to think Sneak Attack is a Special
Ability, and not just a Backstab whilst Hiding/Sneaking like I
normally do?

...BUT I was back in HHK today with my lvl 27 Rogue and instead of
backstabbing the Gnolls for 30 to 35 regularly, as I did the previous
day, I was now backstabbing regularly for 60 to 80 and had a fair few
backstabs of 90 to 100+  :)  My record for the session was a 114, and
in one fight I did 3 backstabs totalling 274!  The improvement in
damage was significant tonight.

Oh, this was using a Grimling Miner Pick, 12 damage, non-magic weapon
as my Primary, and not a " uber" weapon.

I'll try again tomorrow and see if it wasn't just a fluke.

Palindrome