The letters, some sexually explicit in content, have been sent to schools, hospitals, mosques, universities, doctors' surgeries and private individuals, leaving some recipients "extremely distressed".
Similarities between the letters made it likely they had come from the same author. "The cursive script used in some of the letters indicates that it may be the writing of an older person. Repeat phrases used also indicate this, especially reference to 'working for 50 years' and regular reference to pensions."
Commonly used phrases in the text include "English parliament", "Exit Europe", "repatriation" and "BBC shutdown". Clippings from the Daily Mail have been included in many envelopes, which often also include cartoon drawings.The hunt has been codenamed Operation Heron; it's not clear whether this is a Brass Eye reference.
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