Located within the outer walls of the Tower of London are the remains of some early 13th century fortifications built by King Henry III.

These include the foundations of Coldharbour Gate which once adjoined the south-west corner of the White Tower as well as the western wall of the Inmost Ward which ran down to the Wakefiekd Tower.

The gate was defended by two cylindrical turrets while the Inmost Ward Wall has arrow loops installed, allowing archers to fire down on attackers who had breached the outer fortifications.

The gate was later used as a prison. Alice Tankerville, who was charged with piracy on the River Thames, became one of the most famous prisoners housed there when, despite having apparently been chained to the wall, she escaped with the help of two guards in 1533 (she was recaptured just outside the Tower).

The gateway was demolished in about 1675 and lead from the roof taken to Greenwich where it was redeployed at the Royal Observatory.

Much of the wall was hidden away behind later buildings but was re-exposed after being bomb damaged during World War II.

Not much remains to be seen today but the foundations do evoke a sense of the royal palace in times past and serve as a reminder that the buildings we see at the Tower today are not all that has existed here.

Other ruins at the Tower of London include the remains of the Wardrobe Tower, which lies at the south-east corner of the White Tower. It is thought to have dated from 1190 and incorporates the base of a Roman bastion.

WHERE: Tower of London (nearest Tube station Tower Hill); WHEN: 9am to 5.30pm (last admission 3.30pm), Tuesday to Saturday; 10am to 5.30pm (last admission 3.30pm) Sunday to Monday; COST: £34.80 adults; £17.40 children 5 to 15 (family tickets available; discounts for online purchases/memberships); WEBSITE: www.hrp.org.uk/toweroflondon/.