What you see nowadays at the Hall is the original portion to the west and a "modern" (circa 1539) wing to the east. Some of the building material, and the complete porch entrance, came from a nearby Nunnery. Surrounding the hall on two sides is a wonderful moat.
As you enter the Hall (it hardly seems right to call it a pub), there's a serving hatch on the right. To the left is the great hall, now used as a restaurant. Following the passage round to the right brings you to the Library Bar which has a cosy pub-like feel, though the furnishings, including a Bishop's Chair, are a cut above what you'd normally expect. You're welcome to visit the rooms upstairs which include a Solar (sitting room) and a tiny former chapel.
The Hall is open every day from 11 to 11 (12 - 10.30 Sunday). On Fridays, Saturdays, Sundays and Bank Holidays there are brewery tours at 12, 1, 2, 3 and 4pm. Food of the very highest quality is available (booking advisable) with local organic produce being used wherever possible. At the bar you'll find three St Peter's beers on draught plus a massive range of their excellent bottled beers, which include some really interesting flavours (the Grapefruit and the Lemon and Ginger are particular favourites of mine). The bottles themselves are unique, the shape being a copy of one from Gibbstown, near Philadelphia, dating from around 1770. You can also buy bottles to take away from the brewery shop.
St Peter's Hall has a reputation for being difficult to find but it's fairly straightforward with the aid of a decent map. From Cambridge take the A14 to Bury then the A143 towards Yarmouth. Shortly after Harleston turn right onto the B1062 then right again at Flixton where you'll pick up signs for the brewery. Don't follow signs for South Elmham Hall which is a different place altogether.
Jerusalem Tavern in Britton Street, Clerkenwell, London, which is well worth a visit.