3. A “late onset illness” is—
(a)a malignancy, or a disorder of the liver, kidneys or central nervous system, in each case which is capable of being caused by an occupational exposure occurring more than [F27 years] before the onset of the illness or the date of death as the case may be;
(b)a mental disorder which is capable of being caused by an incident occurring more than [F27 years] before the onset of the illness; or
(c)a mental disorder capable of being caused by an incident occurring less than [F37] years before the date of onset of the illness, which disorder is capable of causing the person suffering from it to be unable to seek medical help for the disorder within [F27 years] of the date of onset of the illness.