The rectangular Norman Keep was the earliest castle construction, originally built by Geoffrey de Clinton and his son.   The walls are up to 16 feet thick, and the entrance would typically have been up an exposed flight of steps to the first floor.   King John increased the height of the Tower by creating an additional floor which includes the fish-tailed arrow loops.

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         The original form of the ground floor Norman openings, shown here for interest, were for security, and air and light, and not for the purpose of shooting arrows.   They were most likely knocked through by Robert Dudley to match the upper floor windows, except with the arches above filled by timber.

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         The two medium sized cast iron cannons are demi-culverins, each weighing up to 1.5 tons.   Their 4-inch calibre barrels were typically about 11 feet long and had an effective range of a mile, firing cannonballs weighing up to 10 pounds (4.5kg) using a charge of black powder.   The development of cannons prompted the demise of the conventional castle in favour of the artillery fortress, a circular or star shaped multi-tiered gun platform of low profile to help deflect enemy fire.   In anticipation of attack by France and Spain, the foundries of Henry VIII used so much bronze for new cannons that there was a world shortage of tin.

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         The forebuilding, or ‘Loggia’, on the western side originated as the 12th century entrance to the tower.   It has been repeatedly altered, finally becoming the fashionable feature of the Elizabethan era by providing access to the garden in the north court.   Its current ruins were partly rebuilt by the Victorians.

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         The dials of the tower clock on two sides of the South East turret were to ‘show the hours’ – each had an hour hand but no minute hand.   Robert Langham, a servant of Robert Dudley and witness to Elizabeth’s visit in 1575, implied that the clock was faulty, since he noted that the hands were only ever ‘firm and fast’ at two o’clock, and the bell ‘sung not a note all the while her Highness was there’.   The bell, which weighed 500 pounds, would normally have sounded the hour.