Prince William and the Duchess of Cambridge will be able to enjoy the big Norfolk skies from their country retreat.

Royal aides have applied to install a glazed roof on the new garden room being built at Anmer Hall, the Grade II Listed mansion which has been given to the couple by the Queen.

In its original planning application the 16ft by 16ft garden room, which adjoins the house's kitchen, had a tiled roof.

Details of the likely interior layout are also revealed in an amended drawing, which shows a 10ft by 6ft table as the room's centre piece.

The garden room is part of a package of alterations to increase security at the 10-bedroom Georgian house and make it suitable for a young family.

A new access road is also being built to the house, two miles from Sandringham House, across what is currently a field next to the village church.

West Norfolk council is also deciding whether to allow an archaeological dig, originally required to be carried out before work on the road could begin as a condition of planning permission, to be waived.

The remains of the original settlement of Anmer, which pre-dates the Domesday Book, are believed to lie close to the church.

Royal officials say the foundations of the road will not be deep enough to disturb any ancient remains. An archaeologist would remain on site and could instruct a dig to be carried out were any important relics found.

Council officials are due to decide in days whether the amendment will be allowed. The change would speed up work on the drive, although alterations to the hall are unlikely to be completed for some months and it is not clear when current tenant Jamie Everett plans to vacate the property.

Other alterations to the house include accommodation for Royal protection officers. Aides have applied to build a generator to ensure security equipment functions in the event of a power cut.

There is also a one-bedroom block, where the Royal couple could accommodate Prince George's nanny.