After the Norman conquest of England in 1066 deer parks became a 'craze' among the new nobility, who had taken over almost all the land held before by the Anglo-Saxons. While the Domesday Book in 1086 only recorded 37 deer parks, by around 1300 there may have been as many as 3,000. Every nobleman wanted a park and many had one, while great magnates and some bishops owned 10 or more and the king could boast as many as 80 to 100. It was all about hunting deer and having venison available for feasts. To be able to present guests with this 'noble' meat instead of the plain beef and pork that common people (sometimes) had was a serious matter of status.
A deer park was usually created in an area of the manor that was not under cultivation or occupied by hayfields or woods managed as coppice. It was called 'waste' (we would now say nature reserve) and often consisted of some open rough grassland or heath and pasture woodland. There were wild growing native trees, mainly oaks. These and some underwood or shrubs were necessary to provide for winter food and shelter. This became especially important with the introduction by the Normans of fallow deer from southern Europe to stock the parks. These animals would not survive the English winter otherwise.
The park was surrounded by a park pale, a ditch on the inside and an earth wall on the outside on top of which was a pale fence of cleft oak. The deer could not scale such a barrier from inside the park, but 'deer leaps' could lure them in from outside, a clever construction. Deer leaps were usually illegal, because it could deprive the king from 'his' deer that roamed free outside, which were mainly the native red deer. Also inside was usually a park or hunting lodge and if this building was moated we can often still recognize this moat as well as lines of the park pale in the form of lanes, field boundaries or even the earth wall of the park pale. We now know where most of these parks were even if few of these traces remain. By analyzing the position of ancient oaks in the landscape we can find out if they stood in a medieval deer park.
My research has established that medieval deer parks were by far the most important form of land use associated with ancient and veteran oaks in England. Some 35% of all oaks in England with a girth >5.99 m are associated with medieval deer parks and of 115 oaks with >9.00 m girth 60 once stood in those ancient deer parks. Of 23 'most important sites' for ancient oaks I have so far identified, 20 were deer parks and 16 of these were medieval. There are many other landscape associations with ancient oaks and for a significant number of these trees the historical context remains unknown, lost in the mists of time. But the medieval deer parks are the main reason why England has so many of these venerable oaks.