[3] The tower, designed by Richard Seifert and engineered by Pell Frischmann, is located at 25 Old Broad Street in the ward of Cornhill.

[4] At 183 metres (600 ft) high, it was the tallest building in the United Kingdom until superseded by One Canada Square at Canary Wharf in 1990.

The National Westminster Tower's status as the first skyscraper in the city was a coup for NatWest, but was extremely controversial at the time, as it was a major departure from the previous restrictions on tall buildings in London.

The site was then the headquarters of the National Provincial Bank, with offices in Old Broad Street backing onto its flagship branch at 15 Bishopsgate.

[8] The final design preserved the Gibson banking hall and the tower's height was reduced to 183 metres (600 ft).

The building was constructed by John Mowlem & Co[9] around a huge concrete core from which the floors are cantilevered, giving it great strength but significantly limiting the amount of office space available.

The cantilevered floors are designed as three segments, or leaves, which approximately correspond to the three chevrons of the NatWest logo when viewed in plan.

The limitations of the design were immediately apparent - even though the building opened six years before Big Bang, and so there was less of a requirement for large trading floors, the bank decided not to locate its foreign exchange and money market trading operation ("World Money Centre") in the tower; the unit remained in its existing location at 53 Threadneedle Street.

The tower also had its own telephone exchange in one of the basement levels – this area was decorated with panoramic photographs of the London skyline, creating the illusion of being above ground.

The upper floors were occupied by the division's executive management, marketing, and regional offices, moving from various locations in the City of London.

The lower floors were occupied by NatWest's Overseas Branch, moving from its previous location at 52/53 Threadneedle Street.

The adjacent annexe building at 27 Old Broad Street was occupied by NatWest's Overseas Branch cashiers and foreign notes and coin dealing operation.

[20] A helicopter using thermal imaging equipment pinpointed the source of the fire, which was on the 45th floor in a glass-fibre cooling tower.