Part of a promotion that Aldi have called the Great British Brewing Co.
Brewed by Hogs Back Brewery.
Described as "A soft and light malt zingy taste with the aroma of Germanic hops and a touch of citrus and honey."
Purchased in Aldi Blackwater/Sandhurst, Surrey however I imagine this is national.
EDIT: I have posted three separate deals for three different beers in this promotion in the event that one of the beers was particuarly bad and not even worth 99p. If Aldi are selling this type of beer at 99p regularly I may have to pop in more often.