The buildings have been designed to comply with the highest current fire regulation standards, say architects, property owners and local government officials. But experts believe the Government will have to take a fresh look at the adequacy of those regulations in the wake of the Manhattan terrorist attacks.
Evacuees from the World Trade Center reported that it took some nearly an hour to get out of the twin towers, which had 110 floors and four staircases each.
'The traffic jam for those leaving the towers was colossal,' says Paul Hyett, President of the Royal Institute of British Architects (RIBA).
Hyett has set up an expert committee, including architects and structural engineers, to study any lessons to be learned from the September 11 outrage.
'One of its terms of reference will be whether we should increase the capacity and number of staircases, their size and even their final destination, and whether, for example, they should exit underground and away from a building not at its ground floor,' Hyett says.
The main original tower at Canary Wharf has 50 storeys and four stairwells. Elsewhere in the Docklands complex the nearly-completed HSBC tower will have two main stairwells running the full height of its 42 floors. The 600,000 square-foot HQ3 building currently under construction will have two emergency staircases serving its 32 floors. However, the two newer buildings do have a concrete core, unlike the Word Trade Center towers, which had steel cores much less resistant to extreme temperatures.
In Frankfurt, the 50-storey Commerzbank tower, the highest office building in Europe, has three staircases.
Elsewhere in the City of London the new Norman Foster-designed tower, known as the 'gherkin', will have two staircases serving 40 floors. Ironically, the tower is designed for Swiss Re, one of the worst-hit reinsurers facing huge payouts after the Manhattan tragedy. It is to go up on the site of the Baltic Exchange, itself destroyed by an IRA bomb.
Another City of London building, the planned Heron Tower which is the subject of a public planning inquiry next month, will also have two staircases, even though its 700-feet elevation will make it the Square Mile's tallest building.
The number of emergency staircases is not the only issue relating to evacuation.
Newer high-rise buildings often feature extra safety measures such as additional sprinklers, pressurised stairwells to keep out smoke - the main killer in a fire - and better fire resistance of lifts to reduce reliance on stairs.
Hyett stresses that 'there is no need for people to be unduly frightened'. But he adds: 'I believe there is a case for thinking about protecting buildings against the type of fire seen when a plane crashes into a building.'
Gordon Masterton, chairman of the structural and building board of the Institution of Civil Engineers, agrees that attention may be paid to 'making the means of escape from a building more robust'. He believes the insurability of tall buildings could become an important driver of building redesign.
'People will see more perceived risk in taller buildings and insurance rates overseas will inevitably rise,' agrees Bronek Masojada, managing director of Hiscox, the quoted Lloyd's underwriter which estimates the terrorist attacks will cost it 20m (€32m).
In the UK, where the Government-backed Pool Re is the sole source of UK terrorism cover, the issue is as much political as economic, says Masojada. 'The 900m Pool Re has would not be enough in the wake of a huge terrorist attack, so it would be prudent to put up the insurance premiums it charges. But the Government may be keen to keep the premium rates stable for public relations reasons.'
Pool Re will not be drawn on whether it will boost rates for terrorism cover or introduce special rates for skyscrapers.
Meanwhile, workers in the City of London and Canary Wharf may be surprised to learn that current UK regulations make no specific provisions at all for the tallest buildings.
Terry O'Neill, a fire safety expert with consultants Butler & Young, says: 'It can take a considerable time for people to get out of a building and perhaps this needs to be looked at.' O'Neill is a former head of the fire engineering group at London Fire Brigade.
The current regulations apply the same fire safety principles to a 30- or 40-storey office block as they do to a 10-storey building. The rules determining the number and width of of stairwells essentially focus on the number of workers on each floor and the distance from each desk to the nearest emergency stairs. They do not focus specifically on building height and the consequent time needed to evacuate fully a tall building. Width, in effect, is more crucial than height.
As Chris Grasby of London architects Grasby O'Neill says: 'Tower buildings have a relatively small footprint so it is not difficult to design them so that they only require two staircases each.'
Spokespersons for both Canary Wharf and Heron Tower insist there is no need to consider adding more staircases.
Asked about the issue of more stairwells, a City Corporation spokesman says: 'They are not going to spend more money, are they? Commercial reality will get in the way.'
However, some experts believe that commercial reality could soon be dictating the opposite. Masterton of the Institution of Civil Engineers says: 'In order to give more confidence to people thinking of renting space, developers might decide to introduce additional safety features above and beyond the existing requirements.'