£7.9m four-storey boutique hotel will overlook Alnwick Castle, Northumberland
Home to Duke of Northumberland Ralph Percy, 62, and wife Duchess Jane, 60
Hotel will boast 47 rooms and restaurant, bar, fitness centre and meeting rooms
Castle has featured as a backdrop for Blackadder, Robin Hood and Transformers
Harry Potter and the Philosopher s Stone and Downton Abbey also filmed there