Sir Jack Zunz, Sir Denys Lasdun, Sir Alastair Pilkington, Cyril Sweett

Sir Jack Zunz (1923-)

Saviour of the Sydney Opera House

Perhaps the single greatest act of Sir Jack Zunz's distinguished career was simply preventing Sir Ove Arup from sending the resignation letter that would have taken Arup off the Sydney Opera House project. Sir Ove was about to send the letter to the client, New South Wales premier Joseph Cahill, when Arup's project leader, Zunz, told him to have a rethink.

The project might have collapsed without Zunz. The original architect, Dane Jørn Utzon, had already resigned after falling out with the client and Arup. Sir Ove was similarly disillusioned by what he saw as decisions that were compromising the quality of the scheme, such as the proposal to locate a car park close to it.

Also, Zunz's leadership helped Arup come up with ways of making Utzon's complicated design stand up. Hall of Fame judge Peter Murray, who wrote the 2004 book The Saga of the Sydney Opera House, says: "Sir Jack provided the patience, the determination and the political nous on the project."

Not that it is fair to say that Zunz has made this list simply for his efforts in Australia. He was the engineer behind the 127 m high Britannic House, which when it was built in the 1960s was London's tallest building; he was chairman of Arup from 1977 to 1989; and even today is advising on the proposed redevelopment of Battersea Power Station in central London.

In his own words: "Utzon, brilliant and wayward, was the catalyst and the inspiration, premier Cahill was the driving force and our role I suppose was to make it all possible."

Three key dates:

1959-1973 The Sydney Opera House
1977 Appointed chairman of Arup
Institution of Structural Engineers Gold Medal

Sir Jack Zunz made sure that Arup held its nerve and stayed on the Sydney Opera House project

Sir Jack Zunz made sure that Arup held its nerve and stayed on the Sydney Opera House project

Sir Denys Lasdun (1914-2001)

Brutalist architect who designed the National Theatre

Sir Denys Lasdun's name will forever be synonymous with the brutalist icon that is the National Theatre on London's South Bank. Although Lasdun began work on it in 1963, the building took 13 years to complete and has divided opinion ever since. In a 2001 opinion poll conducted by the Today programme, the National featured in the top five of the most liked, and most disliked, British buildings.

But it would be wrong to remember Lasdun just for the National Theatre. Keeling House in Bethnal Green, east London, showed the architect, like many in the modern movement, striving to create better social housing. The University of East Anglia built between 1962-68, is classic Lasdun, a Le Corbusier-inspired amalgam of multi-storeyed raw concrete blocks and ziggurats. The reverence with which the library was extended, over 19 years and several abortive schemes, shows how architects fear altering his works.

Lasdun's own academic career was cut short, leaving the Architecture Association without a diploma. Fortunately, his talent was spotted by Wells Coates, one of the leading lights of the modernist movement in the first half of this century. In the 1930s and 1940s, he worked for Berthold Lubetkin's Tecton practice, where he worked on the penguin pool at London Zoo, before setting up his own firm.

Loved or loathed, the champion of brutalism will long be remembered.

In his own words: "Architecture, for me at any rate, only makes sense as the promoter and extender of human relations."

Three key dates:

1963-76 Design and construction of the National Theatre
The University of East Anglia
RIBA Gold Medal

Sir Denys Lasdun’s National Theatre is loved and loathed in equal measure

Sir Denys Lasdun’s National Theatre is loved and loathed in equal measure

Sir Alastair Pilkington (1920-1995)

Chairman of Pilkington and great industrial inventor

Sir Alastair Pilkington is arguably the construction industry's greatest inventor in the post-war era. Although, as is often assumed, he was not directly related to the Pilkingtons, it was Sir Alastair that turned their family business, founded in 1826, into a global name.

Having survived a prisoner of war camp from 1942-45, Sir Alastair joined Pilkington Brothers, as the company was then known, soon after his return to the UK. In 1952, he revolutionised the glass industry by creating the so-called "float" system of producing the material. By floating glass on a river of molten tin, the product could be produced cheaply and polished to a high standard without putting it through rollers to flatten out. The tin melted any deficiencies and the absence of rollers meant that new faults would not be introduced to the glass.

"It was a matter of trial and error," says Tom Grundy, who worked with Sir Alastair on perfecting the process. "For years we kept improving and improving and improving the process" - until, in 1959, the company was able to license the product to companies around the world, eventually earning it £600m.

Sir Alastair Pilkington explains to colleagues his float system of making glass …

Sir Alastair Pilkington explains to colleagues his float system of making glass …

Pilkington risked as much as £100,000 a month developing the process, but the family's faith in Sir Alastair paid off. The company grew into one of the world's leading materials brands in the 1960s, and eventually more than 80% of all glass was produced using the float process.

Sir Alastair became a well-known figure outside his own industry - he was Pilkington chairman between 1973 and 1980, had his picture hung in the National Portrait Gallery, was a Bank of England director for six years, and served as Chancellor of the University of Liverpool for the last year of his life.

In his own words: Throughout the 1950s, when Pilkington was perfecting the float glass process, everyone kept asking him "When will you succeed?" He would always reply: "We will know the answer to that only when we have succeeded."

Three key dates:

1952 Invented the float glass system

1970 Knighted

1973 Appointed chairman of Pilkington

… and in later life when he was boss of Pilkington

… and in later life when he was boss of Pilkington

Cyril Sweett (1903-1992)

Champion of computers in construction and founder of consultancy Cyril Sweett

In Cyril Sweett's time a computer was a giant beast occupying a whole room of its own, swallowing reams of "punch tape" and requiring about 16 men to tame it. For some QSs, even scarier was the machine's ability to produce bills of quantities, which they thought likely to make them redundant.

But Sweett was undaunted. The firm he founded in 1928 was among the first QS outfits to have its own in-house computer. He told Building in 1979: "They say we're committing suicide but once you start a system you've got to get on with it. If we don't do it, someone else will."

Francis Ives, Cryil Sweett's chairman, remembers: "He knew our profession was perfectly suited to upgrade itself from its traditional background to something state of the art."

Sweett's modernising influence also extended into design. He was the only non-architect to belong to the MARS group of modernist designers. His work with them included the QSing on the iconic modernist De La Warr Pavilion at Bexhill-on-Sea in east Sussex, designed by Erich Mendelsohn.

His admirers include Hall of Fame judge Rob Smith, who says, "In the early 1970s I remember him showing me how his computer system for bills of quantities worked. It was way ahead of anything else in the market.

His was one of main firms you considered as a student when leaving college in the early 1970s."

His later projects included further cutting schemes such as London's Euston Tower.

In his own words: "Some of the bigger firms don't think computers are a good idea, but I think they are wrong." History proves Cyril Sweett right …

Three key dates:

1928 Founded Cyril Sweett
1935 The De La Warr Pavilion, Bexhill-on-Sea
1970 Euston Tower, London