Tower 42 (then known as the NatWest Tower) was the tallest building in the United Kingdom for 10 years, from its completion in 1980 to the topping-out of One Canada Square in November 1990.

National Westminster Bank initially planned a tower of 137m (450ft), but after it retained Richard Seifert as chief architect in 1964 he submitted a preliminary design at 197m (647ft). The proposal called for demolition of two historic buildings - the City of London Club (1834) and the small National Provincial Bank. After prolonged investigation, in 1964 the Environmental Secretary upheld a preservation order on the banking hall, but permitted demolition of the City of London Club, and the tower's height was reduced to 183m (600ft).

The footprint of Tower 42 was designed to resemble the logo of the National Westminster Bank, for whom the tower was built. NatWest vacated the building in the aftermath of an IRA bombing on April 24th, 1993, which ripped through the City's financial district, causing damage to this and several other office buildings.