Question: when was the tower of london finished being built
[{'answer': '1078', 'provenance': [{'wikipedia_id': '31165', 'title': 'Tower of London', 'start_paragraph_id': 1, 'start_character': 523, 'end_paragraph_id': 1, 'end_character': 527, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31165', 'title': 'Tower of London', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 1156, 'bleu_score': 0.9904073966945661, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8209786580967261392}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31165', 'title': 'Tower of London', 'section': 'Section::::Foundation and early history.\n', 'start_paragraph_id': 24, 'end_paragraph_id': 24, 'meta': {'evidence_span': ['At the latest, it was probably finished by 1100 when Bishop Ranulf Flambard was imprisoned there.', "Most of the early Norman castles were built from timber, but by the end of the 11th century a few, including the Tower of London, had been renovated or replaced with stone. Work on the White Tower which gives the whole castle its name is usually considered to have begun in 1078, however the exact date is uncertain. William made Gundulf, Bishop of Rochester, responsible for its construction, although it may not have been completed until after William's death in 1087. The White Tower is the earliest stone keep in England, and was the strongest point of the early castle. It also contained grand accommodation for the king. At the latest, it was probably finished by 1100 when Bishop Ranulf Flambard was imprisoned there. Flambard was loathed by the English for exacting harsh taxes. Although he is the first recorded prisoner held in the Tower, he was also the first person to escape from it, using a smuggled rope secreted in a butt of wine. He was held in luxury and permitted servants, but on 2 February 1101 he hosted a banquet for his captors. After plying them with drink, when no one was looking he lowered himself from a secluded chamber, and out of the Tower. The escape came as such a surprise that one contemporary chronicler accused the bishop of witchcraft."]}}]}, {'provenance': [{'wikipedia_id': '31165', 'title': 'Tower of London', 'section': 'Section::::Abstract.', 'start_paragraph_id': 1, 'end_paragraph_id': 1, 'meta': {'evidence_span': ['The White Tower, which gives the entire castle its name, was built by William the Conqueror in 1078 and was a resented symbol of oppression, inflicted upon London by the new ruling elite', 'The White Tower, which gives the entire castle its name, was built by William the Conqueror in 1078 and was a resented symbol of oppression, inflicted upon London by the new ruling elite.', "The Tower of London, officially Her Majesty's Royal Palace and Fortress of the Tower of London, is a historic castle located on the north bank of the River Thames in central London. It lies within the London Borough of Tower Hamlets, separated from the eastern edge of the square mile of the City of London by the open space known as Tower Hill. It was founded towards the end of 1066 as part of the Norman Conquest of England. The White Tower, which gives the entire castle its name, was built by William the Conqueror in 1078 and was a resented symbol of oppression, inflicted upon London by the new ruling elite. The castle was used as a prison from 1100 (Ranulf Flambard) until 1952 (Kray twins), although that was not its primary purpose. A grand palace early in its history, it served as a royal residence. As a whole, the Tower is a complex of several buildings set within two concentric rings of defensive walls and a moat. There were several phases of expansion, mainly under kings Richard I, Henry III, and Edward I in the 12th and 13th centuries. The general layout established by the late 13th century remains despite later activity on the site."]}}]}]