A gift of a former PPR to a daughter is being contemplated. As W is younger and healthier it makes sense for H to gift his 50% to W so she can make the PET for IHT purposes (HMRC don't usually treat this as an assocaied operation - see IHTM14833).
It appears that W can still rely on the fact that she's owned a 50% interest in the property during the time it was used as the couple's PPR, with the additional 50% interest being effectively an enhancement of her existing interest.
Section 222(7) TCGA 1992 states the period of ownership where the individual has had different interests at different times shall be taken to begin from the first acquisition taken into account in arriving at the expenditure which under Chapter III of Part II is allowable as a deduction in the computation of the gain. Subsections (a) & (b) are not in point because the property is not currently their main residence, so W does not inherit H's PPR history, but it would appear she can rely on her original interest such that the PPR history will apply to the contemplated disposal of a 100% interest to her daughter. The property has not been let.
Do readers agree?