In this Chapter "ten-year anniversary" in relation to a settlement means the tenth anniversary of the date on which the settlement commenced and subsequent anniversaries at ten-yearly intervals, but subject to subsections (2) to (4) below.
The ten-year anniversaries of a settlement treated as made under section 80 below shall be the dates that are (or would but for that section be) the ten-year anniversaries of the settlement first mentioned in that section.
No date falling before 1st April 1983 shall be a ten-year anniversary.
Where—
the first ten-year anniversary of a settlement would apart from this subsection fall during the year ending with 31st March 1984, and
during that year an event occurs in respect of the settlement which could not have occurred except as the result of some proceedings before a court, and
the event is one on which tax was chargeable under Chapter II of Part IV of the Finance Act 1982 (or, apart from Part II of Schedule 15 to that Act, would have been so chargeable),
the first ten-year anniversary shall be taken to be 1st April 1984 (but without affecting the dates of later anniversaries).