Spuds, how do you keep the slugs out?

The only time I have grown spuds without keel slug damage (apart from my potted plants of course) was when I grew them in depresions in soil filled with uncomposted hoss muck. It was given to us as muck but was basically sawdust soaked with hoss wee with a smigen of poo which must have been cleaned out of the stables. As well as holding the moisture the potatoes I harvested were clean s a whistle and slug free.

All I did was take a couple of trowel fulls of soil from each planting station, put a handful of 'muck' in and topped up in a small heap with muck.

I have grown Kestrel in the past which does have a degree of slug resiistance. What worries me is whats' in em tht the slugs don't like!