Which British hop variety is characterized by its low bitterness?

The British hop variety known for its low bitterness is Fuggle. This variety is primarily used for its aromatic qualities rather than its bitterness. It contributes earthy, herbal, and woody notes to a beer, which makes it an excellent choice for balanced ales, particularly English styles like pale ales and stouts.

In contrast, Northern Brewer and Admiral are typically used for their higher alpha acid content, producing more bitterness in the finished beer. Challenger also has a higher level of alpha acids, making it a popular choice for both bittering and aroma, but it doesn't match the specifically low bitterness profile of Fuggle. Thus, Fuggle's distinctive low bitterness alongside its contributing flavors makes it the best choice in this context.