The MDA made fully developed and tested American designs available quickly and cheaply. The first of these was the Mark 28, which was "Anglicised" and manufactured in the UK as Red Snow. Exact copies of American designs were not pursued; the high explosive used in American warheads were more sensitive than British high explosive, and had caused fatal accidents in the US. Its use was not contemplated in the UK after an accident at Aldermaston on 28 February 1959 when two men were killed after a piece of British high explosive fell from a lorry. British high explosive was also bulkier, so a redesign was required.