Who created the gardens at Acorn Bank?

Acorn Bank is a sixteenth- to eighteenth-century Westmorland gentry house surrounded by walled gardens containing orchards, a nationally important herb garden and Italianate sunken garden. The wider estate contains eighteenth-century gypsum mines and a working watermill with medieval origins. In 2019, a project to investigate the origin and development of the gardens was undertaken in order to understand which elements are original, and which are later additions and alterations. The age of the sunken garden was of particular relevance ahead of planned restoration work.
History of the site
Acorn Bank has been occupied since the twelfth century; previous owners include the Knights Templar. Between the mid-sixteenth and late eighteenth century, it was owned by the Dalstons, a prominent local family. It then passed to the Boazman family who mostly leased it, before selling in 1930 to wealthy socialite and author Dorothy Una Ratcliffe (known as ‘D.U.R’) and her second husband, Capt. Noel McGregor Phillips.
In 1950, D.U.R gifted the property to the National Trust. But who, amongst all these owners, created the walled garden and the beautiful sunken garden within it?
Clues...
A reference in National Trust archives refers to enclosure in ‘1611 at the time of the Dalston family’. If accurate, then Christopher Dalston (1586-1634) began the garden wall. The variable brickwork bond seen closest to the house supports this early date.
A mid-seventeenth century reference to apricots grown at Acorn Bank reveals that the heated fruit wall in the garden must have been well-established by then.
Christopher’s son and daughter-in-law, John and Lucy (neé Fallowfield), significantly extended the house in the 1670s. At the end of the seventeenth century, the east elevation was described as constructed ‘according to the Tuscan manner’. Acorn Bank had been altered in keeping with Continental ideas about architecture and design.
Nineteenth-century maps suggest formal planting, possibly including a parterre, within the walls. This supports an early origin; by the mid-eighteenth century the creation of new formal gardens had ceased, now people desired uninterrupted pastoral vistas.
Boazman family photographs reveal that D.U.R. made no alterations to the form of the sunken garden.
Seventeenth-century gem
Christopher Dalston probably began construction of the walled garden around 1611 but his son and daughter-in-law, John and Lucy, are now thought to be responsible for creating the sunken garden. They transformed Acorn Bank from an early post-medieval manor to a classical Westmorland gentry home. Their Tuscan-style east range was clearly intended to be seen from a fashionable Italianate sunken garden, and vice versa.
Since many formal gardens were lost as a result of the later eighteenth-century fashion for uninterrupted ‘natural’ views, the sunken garden and walls at Acorn Bank represent an important survival of the seventeenth-century landscape.