This type of medieval pottery is known as "Cheam ware", part of the broader tradition of "Surrey white ware", so called because the clay used becomes whitish when fired. The shape is called "biconical" because it has a conical base with a conical shoulder (hence the name) and it usually has a straight, vertical neck but no pouring lip. There is usually a small blob of green or yellow glaze on the neck or shoulder opposite the handle.
Looking at suburban Cheam today it is amazing to think that in medieval times this was a hive of industry with multiple pottery kilns turning out hundreds of jugs, cooking pots and storage vessels for the London market. If you know what to look for, the pits which provided the clay still exist - behind Cheam church and within Seears Park. Later on, the local clay was used for making bricks - the last brickyard closed in the mid 1930s, and all that land was eventually covered with houses.
You can see Cheam pottery at Whitehall Museum, Cheam, and the Museum of London.