The Greater London metropolitan area contains the most skyscrapers in the European Union. Few skyscrapers were built in London before the late 20th century, owing to restrictions on building heights originally imposed by the London Building Act of , which followed the construction of the storey Queen Anne's Mansions. The lifting of height restrictions caused a boom in the construction of tall buildings during the s. With the precedent set by the towers of Canary Wharf and with the encouragement of former Mayor of London Ken Livingstone , a renewed trend for building tall has been established in recent years. This includes spires and architectural details but does not include antenna masts. The "Year" column indicates the year in which a building was completed.