strong and unanimous view ... that the Aberfan disaster could and should have been prevented. ... the Report which follows tells not of wickedness but of ignorance, ineptitude and a failure in communications. Ignorance on the part of those charged at all levels with the siting, control and daily management of tips; bungling ineptitude on the part of those who had the duty of supervising and directing them; and failure on the part of those having knowledge of the factors which affect tip safety to communicate that knowledge and to see that it was applied.