I accidentally flattened the 12V battery and LKA reactivated. I tried everything to turn it off but failed. The steering wheel icon appeared and the steering wheel was 'jamming' on winding roads and, once, tried to send me into a ditch. This isn't a 'safety feature' when that happens.
I finally resolved it by turning off the Driver Assistance (the speed limit/adaptive cruise control one) which seems to, on the face of it, have nothing to do with it. The steering wheel icon then disappeared. I then turned it back on with the things I wanted and it's fine (apart from having to turn the audible alarm off everytime).