(1) Subject to this Act, a person shall be entitled to unemployment benefit in respect of any day of unemployment (in this Part referred to as "a day of unemployment") which forms part of a period of interruption of employment, if -
(a) he is under pensionable age on the day for which the benefit is claimed,
(b) he proves unemployment in the prescribed manner,
(c) he satisfies the contribution conditions in section 43, and
(d) he has sustained a substantial loss of employment in any period of 6 consecutive days.
(2) The circumstances in which a person is to be regarded, for the purposes of this Chapter, as having sustained a substantial loss of employment shall be specified in regulations, and different circumstances may be specified for different provisions of this Chapter.
(3) A person shall not be entitled to unemployment benefit for the first 3 days of any period of interruption of employment.
(4) For the purposes of any provision of this Act relating to unemployment benefit -