During construction physicist Terence Price considered the possibility of a fuel cartridge splitting open if, for example, a new cartridge were inserted too forcefully, causing the one at the back of the channel to fall past the relatively narrow water channel and break on the floor behind it. The hot uranium could catch fire, and the fine uranium oxide dust would be blown up the chimney and escape. Raising the issue at a meeting he suggested filters be added to the chimneys but his concerns were dismissed as too difficult to deal with and not even recorded in the minutes. Sir John Cockcroft, leading the project team, was sufficiently alarmed to order the filters. They could not be installed at the base as construction of the chimneys had already begun, and were constructed on the ground then winched into position at the top once the chimney's concrete had set. They became known as "Cockcroft's Folly" as many regarded the delay they caused and their great expense to be a needless waste. During the fire the filters trapped about 95% of the radioactive dust and arguably saved much of northern England from becoming a nuclear wasteland. Terence Price said "the word folly did not seem appropriate after the accident".