IHTM35085 | How many variations can be attempted?: link between s.142 and s.144
From HM Revenue & Customs · Inheritance Tax Manual
You may accept that
there can be an IHTA84/S142(1) variation or disclaimer after an IHTA84/S144 event, such as the exercise by trustees of powers of appointment and advancement, and
an IHTA84/S144 event after an IHTA84/S142(1) variation has created a discretionary trust, or a disclaimer has caused property to be added to a discretionary trust set up under the will.