8(1)Where—
(a)a person has a progressive condition (such as cancer, multiple sclerosis or muscular dystrophy or infection by the human immunodeficiency virus),
(b)as a result of that condition, he has an impairment which has (or had) an effect on his ability to carry out normal day-to-day activities, but
(c)that effect is not (or was not) a substantial adverse effect,
he shall be taken to have an impairment which has such a substantial adverse effect if the condition is likely to result in his having such an impairment.
(2)Regulations may make provision, for the purposes of this paragraph—
(a)for conditions of a prescribed description to be treated as being progressive;
(b)for conditions of a prescribed description to be treated as not being progressive.