the nut i am refering to on a ford ka 2001 is the large nut in the centre of the rear hub that holds the whole hub on it is actually four nuts all locked togeather the two outer ones are very thin and are dished slighlty the size is 27 mm they are all locked togeather by a lock tab that locks all 6 sides off the nuts, thanks Nigel for your info

Graham Price, July 2009

There are 2 types of Hub nuts on KA's I've found. A smaller nut with the spring clip holding all 6 sides and a larger with only 2 spring clips on 2 opposing sides. These are different sizes, one taking a 30mm socket and the other a 32mm.
From what I understand these need to be tightened to 295 Nm.

gargravarr, September 2013