Chris Bolt, Swift's chief economic adviser and effective deputy, filled the regulator's position, in July 1999 a new rail regulator began a five-year term, starting a much tougher regulatory era. Tom Winsor, the new rail regulator, had been Swift's general counsel (1993–95), and adopted a more interventionist and aggressive regulatory approach. The relationship between the two parties was reportedly stormy at times; in April 2000, it was reported in The Guardian that "Railtrack is adopting a deliberate 'culture of defiance' against the rail regulator". Gerald Corbett, Railtrack's chief executive at the time, and Winsor did not share the same vision for the network. Railtrack resisted regulatory action to improve its performance, and as the regulator probed ever more deeply, serious shortcomings in the company's stewardship of the network were revealed. Winsor informed Railtrack that if it did not improve passenger train performance by 12.7 percent by March 2000, the company would have to pay fines out of its profits. On 17 October 2000, the Hatfield rail crash occurred; this would prove to be the defining moment in Railtrack's subsequent collapse. The cause of the fatal accident was quickly determined to be an infrastructure-related failure, and thus within Railtrack's remit. In Hatfield's aftermath, major repairs were undertaken across the whole British rail network which were estimated to have cost in the order of £580 million. Railtrack had no idea how many potential Hatfields were waiting to happen, nor did they have any way of assessing the consequence of the speed restrictions they were ordering, largely because the majority of the engineering skill of British Rail had been sold off into separate maintenance and renewal companies. These restrictions brought the railway network to an almost total standstill and drew significant public ire. According to Wolmar, the Railtrack board had panicked in the wake of Hatfield. Around this time, regulatory and customer pressure on Railtrack audibly increased while the company's share price fell sharply as it became apparent that there were serious shortcomings in the company's ability to tackle and solve fundamental problems with its core activities. During February 1999, a significant fall in Railtrack's share price occurred in response to the company's launch of a bond issue intended to finance the West Coast Main Line modernisation and Thameslink Programmes. The modernisation of the West Coast Main Line had suffered from spiralling costs, rising from an estimated £2 billion to roughly £10 billion.