The ventilated façade system consists of overlapping flat panels which resemble snakeskin, obviating the need for curved panels; indeed the exterior is expressed without a single piece of curved glass.

The base of the tower exhibits a curvaceous canopy which billows out in the manner of the bottom of a pair of flared trousers.

The top of the tower should sway by only about 5 centimetres (2 inches).

The façade is ventilated to counter solar gain and facilitate the use of natural ventilation.

The design maximises the use of natural light reducing dependence on electric lighting.

The building has 52 office floors with financial trading floors sited on levels 3 to 9.

Level 57 is double height.

An earlier proposal for a 216m tall, 50-storey tower designed by Murphy/Jahn Associates on the site of 6-8 Bishopsgate and 22-24 Bishopsgate was abandoned following opposition from English Heritage over the impact on the view of St. Paul's Cathedral looking east along Fleet Street.

The scheme was initially proposed to be 307.25m tall with 64 storeys and a total floor area of 140,147sq m. Following objections from the Civil Aviation Authority, the height was reduced in December 2005 by 19.35m/4 storeys.

The design of the top resembles a helter-skelter, hence the tower's nickname.

The bottom three storeys of the tower are publicly accessible; there is also a sky lobby and restaurant on the 43rd floor which are London's highest public vantage point.

A planning application was submitted on 1 December 2006 to make a series of revisions to the scheme in order to increase the overall floor area. The changes retain the same building envelope, but include 3 additional floors, a revised Sliver building, changes to the cladding and a larger basement.

The building incorporates biomass heating and ground water heat exchangers.

Features a high performance triple glazed façade and combines both natural and mechanical ventilation to reduce carbon emissions and energy consumption.

The tower has 90,000 photovoltaic cells which are integrated into around 2,000 sq m of the façade and generate 200 kilowatts of electricity.

All of the office floor plates can be split to house two tenants on one floor and all floors can be configured for cellular or open-plan occupation.

The building has 60 main 2.4 metre (7.8 feet) piles descending to a depth of 60 metres (197 feet), each of which required concrete to be poured continuously for 13 hours.

The height was determined by the flight path leading to London's City Airport.