preferential treatment, my answer would have to be that a warning of 90 seconds may enable adequate protection to be provided against a very large and concentrated calamity risk that would be created if the tubes were flooded but a warning of 90 seconds duration could do little to protect the victims of a rocket incident of the ordinary type and must occasion great waste of working time and unnecessary alarm to the public. II. Removal of Shelterers There are some 15 L.P.T.B., as well as other premises, liable, if the worst happens, to be flooded within 15 minutes of the rupture of the under River Tubes.