In the article 'Tests cast doubt on original WTC fire specs' (NCE 2 September) you state: 'The second [fire test carried out by the US Department of Commerce's National Institute of Standards & Technology] used the [cementitious fire protection coating] thickness of 13mm specified by the towers' designer Leslie Robertson'.
I did not specify the fireproofing material, the thickness of the fireproofing material or the method of application of the fireproofing material. In short, this was the work of others.
Only now is the truth emerging regarding the structural integrity of the twin towers. As the story unfolds, you will find that the designs produced by us exceeded by far the requirements of any building code known to us and that, following the aircraft impacts, the towers would have stood indefinitely were it not for a second significant event (the fires).
You have cast a shadow over my designs for the World Trade Center, a shadow that is not in any way deserving. Also, as your story finds its way into New York, you will be adding further agony to those who lost loved-ones in this terrible event.
The opening paragraphs of your article are also non-factual and sensationalistic and so not worthy of a publication containing in its banner the word 'engineer'.
Leslie E Robertson, xxlerxx@yahoo. com.
NCE accepts that Leslie Robertson was not named as the specifier of the fire protection system in the US National Institute of Standards & Technology (NIST) report that formed the basis of the story published and we apologise for any distress this may have caused.
NIST has since stated that it has not been able to establish 'exactly how the original thickness was arrived at or who came up with the figure.'
It added: 'We now believe the thickness of the fireproofing really does not matter. The building collapsed because the initial impacts knocked off so much fireproofing that key sections of the steel frame were left completely unprotected.'
(NCE 21 September)