The land behind King John's House was part of the medieval holding, but was only acquired for the Trust in 1991. The garden is thus very new. It is run by a sub-committee under the title "Friends of King John's Garden". The aim has been to create a period garden reflecting the historic significance of the site, where there were once 18th century cottages as well as the remaining medieval stone house and its timber-framed extension. Flowers, shrubs and trees are researched to ensure that they are compatible with these buildings. The garden is level with wide gravel paths leading from flowery meads to a waterside garden and on to a herb garden and more formal flower beds, all featuring plants known in this country before the early 1700s.

A focal point of the garden is a large courtyard, complete with pump and sheltered by the surviving spine wall of the 18th century cottages. This is being used at various times for a range of activities, including plant sales, quilt stretching, poetry reading and, most ambitiously, a Shakespearean production.