Editing SIS Building (section)

===Background===
Previously based at [[54 Broadway]],<ref>{{cite book|url= https://books.google.com/books?id=vCPGrWeK04gC&pg=PA12   |title=Jubilee Line Extension From Concept to Completion|first= Bob|last= Mitchell |year=2003|publisher=Thomas Telford |isbn=978-0727730282|page=12}}</ref> the SIS relocated to [[Century House, London|Century House]], a 22-storey office block on [[Westminster Bridge Road]], [[Lambeth]], near [[Lambeth North tube station|Lambeth North]] and [[London Waterloo railway station|Waterloo]] stations, in 1964.<ref name=TelegSep2300/> Its location at Century House was classified information, though ''The Daily Telegraph'' reported that it was "London's worst-kept secret, known only to every taxi driver, tourist guide and KGB agent".<ref name=TelegSep2400/> Century House was described as "irredeemably insecure" in a 1985 [[National Audit Office (United Kingdom)|National Audit Office]] (NAO) report with security concerns raised in a survey; the modernist building was made largely of glass, and had a petrol station at its base.<ref name=TelegSep2400/>{{sfn|Corera|2012|p=321}} Security concerns combined with the remaining short leasehold and cost of modernising the building were important factors in moving to a new headquarters.<ref name=TelegSep2400/>