The chief executive of High Speed 2, Alison Munro, has dismissed the claim that the rail project will cost £80 billion - more than double the official estimate - as "absurd".
She told ITV News that she "doesn't recognise" the figure allegedly quoted in a report by the Institute of Economic Affairs, and that she is confident the cost will not overrun.
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Christopher Kerr murdered 15-year-old Michael McIlveen in 2006.
Police warned people not to approach the 32-year-old if they spotted him.
A witness said that the animals may have been spooked by the sound of a horn.