How benches and public art became first line of defence against terrorists

Official advice issued to architects on building the bomb-proof structures of the future

New anti-terror design guidance was issued to architects in Britain this week, and some are already worried it will contribute to a "Fortress Britain" mentality which will change the look of key points in our towns and cities. But by how much? Is the recently announced design of the new US Embassy for London, which resembles a moated cube wrapped in seersucker body armour, really the shape of things to come?

The new guidance, issued this week by the Royal Institute of British Architects (RIBA) with input from the Home Office and the National Counter Terrorism Security Office, offers broad-spectrum advice that picks up on design strategies which have become standard procedure in the City of London, where the risk of terrorist bombings pose by far the most significant threat to the economy.

The City's director of planning, Peter Rees, said: "Modern terrorism is about terrorising people, rather than causing massive collateral damage to buildings. They want to kill or main as many people as possible. And it's aimed at heavily crowded situations.

"The City of London has addressed this issue since the IRA bombings of the 1990s. But it's not just cities like London and New York that must design against terrorist attack. The risk is just as great, or perhaps greater, in less well-known places and situations."

Leaving aside the fact that many of our town and city centres are already architecturally terrorised by fortresses of shopping, it's actually a case of so far so good. In the City of London, densely riddled with infrastructure, IT and electricity conduits, and scores of buildings generating tens of millions of pounds in earnings a day, the well-established security design measures are barely noticeable.

The most fundamental anti-terrorist design requirement is not the specification of anti-blast glazing or super-strong structures, but the prevention of ram-raids by lorries packed with high explosives – which is why the frenzied corporate appetite for tall, distinctive buildings is putting anti-terror design to its biggest test. It's not the height of these buildings that is the main issue, but the vulnerability to catastrophic damage causing civilian casualties at street level.

This is why there are so many apparently incidental pocket-sized public spaces sporting heavy stone benches or chunks of public art in key positions: they would force a terrorist's vehicle travelling at high speed to slow down significantly at key approaches to important buildings. Convivial landmarks – often a relief to the City's architecture – are doubling as lines of defence.

The terror-proofing of major transport interchanges has become an equally pressing issue, and the £300m modernisation of King's Cross station by lead architects John McAslan + Partners is currently the absolute case in point. Project architect, Simon Goode, said: "The need to produce increasingly secure buildings and spaces must not result in the design of bunkers and bastions with standardised blast glazing, cheap cladding and low-spec interiors. Buildings are for the use of ordinary people with ordinary pursuits. They must not become the depressing embodiments of worst-case scenarios."

A key design tactic at King's Cross is the creation of a new public plaza, about the size of Trafalgar Square, in front of the station where three major roads come together. The plaza will undoubtedly look charming and be a lovely addition to London life, but its covert design intention is stark: it's there to prevent terrorist ram-raids.

It's hard to predict how quality may be affected by increasingly twitchy anti-terrorist design requirements. In the foreseeable future, the changes are unlikely to be very noticeable.

But that could change overnight, and forever, if a major ground-level or subsurface terrorist attack produced devastating results.

Safe havens: Designed to foil attack

30 St Mary's Axe (The Gherkin)

Designed by Foster & Partners, the building's steel framed diagrid creates outstanding structural stability – which is more usually achieved, post 9/11, by impact-absorbing "ductile" joints. The diagrid envelope is linked to main beams, ensuring overall structural stability in the event of sustaining major damage.

National Assembly for Wales

Designed by Rogers Stirk Harbour, the anti-terrorist measures relate to the public plaza around the building, which creates a landscaped "stand-off" zone, supported by a series of staircases, strengthened street furniture and vehicle and security checks.

US Embassy proposal, London

Is it architecture, or a svelte bunker? The design, by Kieran Timberlake, was criticised by two of the design competition jurors, Lord Rogers and Lord Palumbo. Getting into the building will almost certainly be as hard, and possibly as unpleasant, as getting through customs at American airports.

Cabot Place, Bristol

A concern was the central public space beneath a glass canopy at the centre of three converging streets. Anti-hostile vehicle street furniture was put on those streets, and side streets were aligned to block direct lines of vehicle entry.