London is in a race to complete major infrastructure projects—an upgraded Tube, an expanded King’s Cross terminal, a cable car flying across the Thames—before the Olympic Games even begin. Call it the “London 2012 Effect.”

You might not think, as you emerge from London’s refurbished Green Park subway station near Buckingham Palace, or glimpse the development going on behind the hugely expanded King’s Cross terminal, that they had much to do with the 2012 Olympics. Nor would you conclude that building an extension to the Tate Modern museum was related to the Games. But these and many more construction projects are all examples of the “London 2012 Effect.”

The Olympic Games gave the city a deadline, and not just for building sports venues. As with many past Olympics cities, the transit system had to be upgraded. More hotel rooms were needed. And a rich cultural program had to be created to celebrate the event. But in London—which was awarded the Games during boom times—the remarkable extent of new and renovated infrastructure and development is, well, Olympian. Projects that were slated to happen anyway were brought forward, such as the upgrade and expansion of the Tube network at pinch-point interchanges like Green Park (Acanthus LW Architects), Farringdon (Atkins and Aedas), and the underground halls at King’s Cross/St. Pancras (Allies and Morrison). Projects that seemed too expensive and ambitious were suddenly approved and built. Even Renzo Piano’s Shard skyscraper (or at least its shell and core) at London Bridge Station will be completed in time to be featured on the Olympic telecasts.

This helps to explain why, in the midst of the UK’s current economic austerity, the state-owned Network Rail was able to recently complete the new Western Concourse of King’s Cross station, the gateway to Northern England and Scotland. The design for a steel-latticework hemisphere by John McAslan + Partners and Arup was gathering a decade-plus of dust when London somewhat unexpectedly won the bid to host the Olympics in July 2005. King’s Cross was already badly congested: The extra space would be even more needed at Games time. The Olympics ensured that the original concept came through largely unscathed.

The project has its flaws but is one of the fine new enclosed public spaces of London, comparable to Norman Foster’s Great Court at the British Museum (2000). It sits alongside an ongoing restoration, also by McAslan, of the rest of the 1852 terminus—originally designed in dour functionalist style with a touch of the Italianate by architect Lewis Cubitt. The project will later include a new public square designed by Stanton Williams [page 78]. All in all, King’s Cross will cost $880 million when complete in 2013.

Because King’s Cross is an historic landmark, the new Western Concourse could not structurally interfere with it. Even Cubitt’s adjacent workaday Great Northern Hotel was deemed worth saving, generating the geometry of McAslan’s scheme and meshing with it at ground level where it becomes a retail arcade. By happy chance, that led to the hemispherical form that is exactly the area required, some three times the size of the previous passenger concourse. Inside, the structure funnels down in front of the original western entrance and ticketing hall. This is not a glass house: Glazing occurs only at the point of the funnel and around the edge. There are some clumsy moments. The mezzanine restaurant at the rear of the space seems a bit too big and crude next to that virtuoso engineering. Overall, delicacy loses out to the necessary blast resistance.

The completion of the McAslan scheme, the earlier transformation of next-door St. Pancras (now London’s European rail terminal), and the reopening of its 1874 Gothic Revival hotel by Sir George Gilbert Scott, opens up 67 acres of former freight yards north of the terminal to a massive development that began in 2006. This is the largest urban regeneration project of recent times in the capital. The completion of King’s Cross station in time for the Olympics is revealing the new privately developed public realm (including 20 new streets and 10 new public spaces) of this former urban wasteland. Companies are planning to move in, the British headquarters of Google rumored to be one. A group of previously neglected Cubitt warehouses, including the Granary, comprises the new $241 million campus of Central Saint Martins College of Arts and Design, by Stanton Williams.

London’s acute shortage of landing capacity for airlines will be cruelly exposed by the Olympics. Heathrow Airport’s cluster of small terminals will become the new $3 billion Terminal 2, with satellites. The whole enterprise, planned to open for London 2012, is running late. The Emirates Air Line, a cable car across the Thames, will be finished in time. Designed by Wilkinson Eyre, it will permanently link two previously unconnected regeneration sites.

It was remarkable just how many non-sporting developments were declared necessary for the Games. The Tate Modern made much of its intention to build its Herzog & de Meuron–designed $347 million extension in time for the Olympics. Two underground galleries in former oil tanks will be ready, but the 11-story aboveground building will not be complete until 2016. So what? Well, the Olympian rush to build was more than a convenient excuse. Perhaps it can be seen as an old-fashioned Keynesian economic stimulus. Without the ripple effect of London 2012, the British economy, now back in recession, would be in even worse shape.

Overall, Londoners will have gained an improved transport system, a large, new public park on the Olympic site, and the economic boost provided by considerable spin-off development. But the poorest boroughs—in East London close to the Games—will remain stubbornly poor, and the rest of the UK outside the development bubble of London will feel very little tangible benefit. Welcome though the Games are for national pride, nobody ever pretended that they alone would be enough to save the national economy.

Hugh Pearman is the architecture critic of the Sunday Times, of London, and editor of RIBA Journal.