The roofs of the White Tower and its turrets were repaired in the 1960s and 1970s . Accumulated dirt was washed from the exterior and the floors inside replaced . Also in this period a staircase was added against the south face of the keep , reopening access through the original entrance . In 1974 , there was a bomb explosion in the Mortar Room in the White Tower , leaving one person dead and 35 injured . No one claimed responsibility for the blast , but the police investigated suspicions that the IRA was behind it . In 1988 , the Tower of London as a whole was added to the UNESCO list of World Heritage Sites , in recognition of its global importance and to help conserve and protect the site . The Tower of London is in the care of Historic Royal Palaces , a charity , and between 2008 and 2011 a £ 2 million conservation programme was undertaken at the White Tower . Repairs were carried out and the keep was cleaned , removing pollution that was causing damage to the structure . The White Tower is a Grade I listed building , and recognised as an internationally important structure . The Royal Armouries still have displays at the White Tower
1974 , there was a bomb explosion
1974 Tower of London bombing
White Tower (Tower of London)