The first floor contains the great hall,—a noble chamber, 51 feet by 24 feet, with walls from 12 feet to 14 feet thick. It is covered by a pointed barrel vault, quite plain, but, with the walls, of excellent ashlar. The height to the crown is about 30 feet. It occupies the whole breadth of the building. In the north end is a mural chamber, 8 feet 6 inches by 7 feet 10 inches, which contains the head of the well-stair from below. This has a door into the hall and another into the entrance passage. This is the passage of the main entrance, 4 feet 7 inches broad, and 14 feet long, having a door at each end, but no portcullis. It is the main entrance to the tower. Outside, it seems to have been approached by a stone arch of about 8 feet span, of which the springing-course is seen under the door-sill. In the vaulted mural passage are the opposite doors, one mentioned already upon the stair-head, the other leading to the kitchen, which occupies the north wing.

At the other extremity of this northern end of the hall a door opens into a well-stair, 7 feet 10 inches in diameter, which here commences, and supplies the upper floor and the roof. The east side of the hall is pierced by two windows, square headed, in deep-splayed arched recesses of 7 feet opening, and 22 feet apart. Besides these, towards the north end is a small light, a mere loop, in a recess of 2 feet 7 inches opening.

The great feature of the hall, after its fine pointed vault, is a grand fireplace, 9 feet broad and 3 feet deep, with a projecting hood of stone, which dies into the wall about two-thirds of the way up, and is supported by two double half-shafts, with bases and carved caps and a flowered band above, all in the Decorated style. This occupies the centre of the south end, and on each side of it, high up, are recesses of 5 feet opening ending in loops of 1 foot. The hood is broken down and the fireplace in decay, but its remains are very striking. Along the west side of the hall are various openings. In the centre is a window recess, 5 feet 10 inches broad and 9 feet deep, from which a side opening leads into a vaulted serving-room, 5 feet by 11 feet, which again opens into the kitchen. In the south end of this side a door opens into the withdrawing-room, and another door into a well-stair, which here commences, and communicates with the upper floors of the south wing, and the roof. Near the north end of this side a low arch or buttery-hatch opened direct into the kitchen. Besides these openings, there are two ornamental recesses. The one a niche in the north wall for a statue, about 5 feet high, with a handsome groined and floriated canopy and a base resting upon a half-shaft, probably for a statue of the patron saint of the family. Also in the west wall, near the fireplace, is a sort of sedile, 4 feet broad, with an ogee canopy, containing on a shield the three cinquefoils, the Borthwick arms. The walls of the hall seem to have been either painted or covered with devices, one of which, “Ye Temple of Honour,” was recently to be seen. Here and in the staircases are many masons’ marks. Two of the doors have heads as of three sides of a hexagon, something like the Berkeley arch.

The Kitchen occupied the first floor of the north wing. It is 16 feet by 22 feet, and is spanned by a large flat arch, throwing the western half into a stone hood, under which the principal culinary operations were carried on. There are three recesses with loops in the north and west sides, one of which is blocked by a later oven. There is also a small fireplace. The entrances are from the main door of the hall and from the serving-room, and between is the buttery-hatch.

The Withdrawing-room occupies the south wing, and is 19 feet by 14 feet. It was entered from the hall and from the well-stair, and has recesses and small windows towards the south and west, besides wall cupboards. The south wall contains, in a vaulted chamber, the head of the staircase from the well-room and its entresol; and in this wall also is a mural chamber, 8 feet by 7 feet, with two doors, a window, and, in its flat slab-covered roof, a shaft, probably for a stove chimney. This is called Queen Mary’s room, and was probably her bed-chamber when she visited Borthwick. This and the larger room are plugged for panelling, and the contiguous doorways from the stairs and the hall had a wooden porch shutting them off in the corner of the room, so that there was a passage either from the Queen’s room or the staircase into the hall without entering the withdrawing-room.

Above the hall, a corresponding space, 51 feet by 24 feet, is divided by a cross-wall into an upper hall and a chapel. The upper hall, 27 feet by 24 feet, has a large fireplace, with a stone hood and flanking shafts, and near it a window, both in the east wall. In the north wall is a large recess and window and a door into the north-eastern staircase. In the west wall is a window in a recess, and a door which leads by a mural passage into the north wing, and into a garderobe in the north wall.

The Chapel, 24 feet by 21 feet, has a recess of 9 feet wide, in which is the east window, a piscina, and an almbry. It had also two south windows, and between them a small fireplace. In its west wall is the entrance-door from the well-stair, and a door, 2 feet above the floor, from the south wing, which probably opened into a raised seat for the lord. Both chapel and upper hall had a flat timber roof, and were 14 feet high.

The room next above these, the third floor of the body, was of the dimensions of the great hall. It had three windows to the east and one to the north, south, and west. It was entered from the well-staircase in the north-east corner, and that of the south wing, and it had a door direct into the north wing. This room has a long, full-centred barrel vault, which rises about 6 feet above the walls, and is, therefore, to the crown, about 15 feet high. It is probable that this great chamber was broken up by partitions, but it contains no fireplace.

Corresponding to these floors in the body are, in the south wing, five,—the first being the withdrawing-room already described, and 13 feet high. The second has two windows, a fireplace, and a mural garderobe, and is about 11 feet high. The third, the same, and is 8 feet high; the fourth has the same arrangements, and, in addition, a door into the private seat of the chapel. It is 17 feet high. The fifth floor has two windows only, and is about 15 feet high to the crown of its vaulted roof. All the chambers in this wing are of the same size, and one over another.

The chambers in the north wing are over, and of the same size with, the first floor or kitchen, the hood and chimney-shaft of which, built against the west wall, passes up through each floor, tapering as it rises. In this wing there are six floors, most having two windows and some a fireplace. The second floor—that over the kitchen—is entered from the eastern well-stair, whence, at 12 feet above the floor of the hall, a mural passage threads the north wall and its window recess, and leads into the chamber. Hence, ascending in the west wall of the hall 10 feet, it reaches the commencement of a well-stair, which leads to the upper floors and the roof. The uppermost and sixth floor is in the vault of the roof, and is lighted by orifices in its gables.