During Alport's tenure as high commissioner, he came under suspicion from the United Nations over his questionable actions before and after the plane crash that killed UN Secretary-General Dag Hammarskjöld.

When the crash was discovered, Hammarskjöld's CX-52 Hagelin cipher was confiscated by the Northern Rhodesian authorities and Alport refused to return it to the UN.

These looters, three local charcoal burners, who testified that the crash happened at night and reported hearing and seeing an explosion in the sky, going against the official story of the crash happening later the next day, were suspected to have been mistreated by Northern Rhodesian authorities and it is suspected that the looted CX-52 never existed and was invented to discredit the men.

Alport's behavior was scrutinized further in 2015 after a new investigation, led by Mohamed Chande Othman, said that his actions suggest 'that he had a reason to seek to refuse to return United Nations property, including Hammarskjöld's CX-52, to the United Nations, although this was eventually done'.

[4] Additional correspondence with Roy Welensky is archived at the Bodleian Library of Commonwealth and African Studies at Rhodes House, University of Oxford.