Some items at the Amazon warehouse have two discounts.
20% OFF and £30 OFF a £100 spend
It's only some items and most possibly an error.
Edit: seems to be on most things in the "Beer, Wine & Spirits" section.
Such a shame this got voted down, as there are some real bargains to be had; it just takes a bit of effort to find them.
Good find just lazy people cannot be bothered to look got lots of champagne & wine for christmas thanks ok