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How many times have you seen photographs of the British pavilion for this year鈥檚 Shanghai Expo and had to look again to make sure they are not computer generated? In the flesh, amid the 200 or more pavilions all jostling for attention on the vast Expo site, it鈥檚 no less dramatic. When the thousands of acrylic fronds get caught in the breeze, it becomes almost hypnotising.

And, as one of the most talked about and visited of all pavilions at the event - and having just last week scooped the Lubetkin prize - it seems to be living up to its task, which is to alter the way the Chinese perceive Britain. Research shows that we鈥檙e seen as a country of tradition and stability, which is no bad thing, says John McManus of the Foreign Office. But as the Chinese economy motors on through the downturn, this isn鈥檛 enough. 鈥淲e鈥檙e not seen as exciting or good at design or forward thinking.鈥�

Keen to drive home the message that there鈥檚 more to Britain than beefeaters and red telephone boxes, the British government has pulled out all the stops. The focal point of its 拢26m investment is the Heatherwick Studio-designed pavilion.

Katerina Dionysopoulou, architect on the scheme, says visitors to expos tend to either remember the building or the exhibition inside. 鈥淲e wanted to combine the two.鈥�

What it came up with was a 20m-high cube-like structure pierced by 60,686 acrylic spikes. Each spike is embedded with a selection of hand-picked seeds sourced from the Kunming Institute of Botany, a partner in Kew Royal Botanic Gardens鈥� Millennium Seed Bank Project. During the day these spikes work like optical fibres bringing light into the interior, while at night tiny LEDs shine along them, making the whole structure glow.

Coming up with the concept though was the easy bit. Some way had to be found of getting it built. The project was delivered as a design and build and the task of project managing it all fell to Mace. This, though, is far from your typical project management job (indeed last week Mace won an award at the CIOB Global Construction Summit in Shanghai for 鈥渙ustanding achievement in construction management鈥�). 鈥淏ecause of the complexity of the project and the different ways of working in China we鈥檝e had to take a very hands-on approach,鈥� says Mark Tranter, associate director. 鈥淲e were working around the clock and through the holidays to deliver it.鈥�

Because it was being constructed in China, Mace had to first bring on board a local technical institute to translate the UK design so that it complied with local regulations and the requirements set down by the Expo organisers. It then had to appoint a main contractor to deliver it.

No-one had constructed a building pierced with tens of thousands of acrylic spikes before and as well as finding a way of constructing it, with a relatively unskilled workforce, there was also the small matter of finding manufacturers to deliver the 1.2 million components needed to make the spikes, many of which had to be hand made.

Obviously none of the Chinese had worked on a spiky pavilion before, so we had to make planning tools that were understandable

Mark Tranter, Mace

Unlike most design-and-build projects, Heatherwick Studio worked closely with Mace and the Suzhong Construction Group throughout the construction phase, providing detail design input - of which there was plenty. The spikes themselves are made out of 7.5m-long acrylic extrusions. On the end that protrudes into the pavilion is a 400mm-long section that was made separately and contains the seeds. These were cast in a mould and then sanded and polished by hand before being adhered to the extrusion. All this work had to be done in China because of the volumes required.

Although the spikes are designed to sway in a breeze, the pavilion needs to be able to withstand a typhoon. So a 25mm-diameter, 5.7m-long aluminium tube was first slid over each acrylic rod. Another 3.2m-long section on top of that allows the spikes to move but gives them enough strength to avoid snapping. Before manufacturing could begin, the spikes underwent rigorous testing and bespoke components had to bedeveloped to create a watertight seal where acrylic and aluminium sections meet.

The cube itself is constructed from a laminated veneer lumber (LVL) skeleton onto which four layers of plywood are fixed - two on the outer face and two on the inner, through which the spikes penetrate.

The LVL was shipped in from north America in 15m-long, 1.2m-deep planks cut and machined to fit exactly in the gap between the spikes. A total of 242,744 holes had to be precisely positioned and aligned through the plywood sheets so that the spikes would follow the form of the structure.

鈥淲hen they arrived on site the whole pavilion was put together like a jigsaw. The tolerances are basically next to nothing and you couldn鈥檛 allow sheets to creep or anything like that as it鈥檚 not practical to go back and change things once you鈥檝e starting installing the spikes,鈥� says Tranter.

When it came to installing the spikes the sequence was essential. Start in the wrong place and you could find yourself trapped in a forest of 8m acrylic wands with no way out.

鈥淥bviously none of the Chinese had worked on a spiky pavilion before, so we had to make planning tools that were understandable and decipherable on site. We set up simple drawings with details of each of the work faces, showing what they needed to achieve in a day and the sequence.鈥�

The starting point was the roof. A gang of workers would start by threading the spikes from the inside to the outside, careful not to impale the person on the receiving end. As the spike emerged, a clamp was slipped over the end, which provides the main fixing to the structure. As Tranter explains, it wasn鈥檛 possible to drill into the aluminium tube as it would weaken the fatigue strength. Once the clamp was in place a rubber cowl was slid over the top and adhered to the plywood to provide a waterproof seal.

Meanwhile, a team on the inside was marking out precisely the distance each spike protrudes into the space and attaching safety fixings to each spike - a small hook-like device that would prevent it falling should the fitting on the outside fail. There was also an LED to install and test before the team could move on to the next one.

One programme-critical activity, however, was the waterproofing. 鈥淏ecause we had a liquid-applied membrane on the outside, this had to cure before you put on the next layer. You couldn鈥檛 just keep going on with the spikes, otherwise you couldn鈥檛 reach these areas,鈥� says Tranter.

About 300 spikes were being installed in a 10-hour shift. But because it was winter and temperatures plummeted to -10潞C, another 38 hours had to be added for the waterproofing to be applied, cured and tested so any leaks could be plugged before moving on. The last spike was installed by the then British foreign secretary, David Miliband, in March 2009. Then it was on with the fit-out work.

So what happens next? Only five of the pavilions have been designed as permanent structures and after the event closes in October most will be demolished and recycled. Only the UAE has designed theirs to be demountable so that it can be shipped home and reused. The idea is that the spikes from the so-called 鈥淪eed Cathedral鈥� will be distributed with educational packs to schools across China. The structure has even been nicknamed the 鈥渄andelion鈥�, to reflect seeds being blown across the country.

However, McManus says that in the past few weeks, and with its popularity soaring, expressions of interest have been put forward by both Chinese and British organisations keen to buy the pavilion and reconstruct it. Although this would seem like an attractive idea, the structure was designed with a six-month service life in mind.

鈥淲e are beginning to look at the intellectual properties and legal side of it. But our preliminary advice on the design life is that you would essentially be building a new one,鈥� says McManus.

If that鈥檚 the case, Tranter might find his services being called on once again.