ests , ▁whilst ▁bar onial ▁cast les ▁were ▁used ▁by ▁the ▁Norman ▁l ords ▁to ▁control ▁their ▁w ides p read ▁est ates ; ▁a ▁fe ud al ▁system ▁called ▁the ▁castle - guard ▁was ▁sometimes ▁used ▁to ▁provide ▁g arr isons . ▁Cast les ▁and ▁sie ges ▁continued ▁to ▁grow ▁in ▁military ▁s oph istic ation ▁during ▁the ▁tw elf th ▁century . ▁ ▁Culture ▁ ▁Art ▁ ▁The ▁Norman ▁con quest ▁introduced ▁northern ▁French ▁art istic ▁styles , ▁particular ▁in ▁ill umin ated ▁manuscript s ▁and ▁mur als , ▁and ▁reduced ▁the ▁demand ▁for ▁car v ings . ▁In ▁other ▁art istic ▁areas , ▁including ▁emb roid ery , ▁the ▁Ang lo - S ax on ▁influence ▁remained ▁evident ▁into ▁the ▁tw elf th ▁century , ▁and ▁the ▁famous ▁Bay e ux ▁T apest ry ▁is ▁an ▁example ▁of ▁older ▁styles ▁being ▁re emp loy ed ▁under ▁the ▁new ▁regime . ▁St ained ▁glass ▁had ▁been ▁introduced ▁into ▁Ang lo - S ax on ▁England . ▁Very ▁few ▁examples ▁of ▁glass ▁surv ive ▁from ▁the ▁Norman ▁period , ▁but ▁there ▁are ▁a ▁few ▁examples ▁that ▁surv ive ▁from ▁minor ▁monaster ies ▁and ▁parish ▁churches . ▁The ▁largest ▁collections ▁of ▁tw elf th - century ▁st ained ▁glass ▁at ▁the ▁C athed r als ▁of ▁York ▁and ▁Can ter bury . ▁ ▁Liter ature ▁and ▁music ▁ ▁Po etry ▁and ▁stories ▁written ▁in ▁French ▁were ▁popular ▁after ▁the ▁Norman ▁con quest , ▁and ▁by ▁the ▁tw elf th ▁century ▁some ▁works ▁on