Contingent gifts are often misunderstood, despite their frequent appearance in wills.
A gift of £1,000 to A when they attain age 25 is exactly that, I the absence of any further provision – they receive £1,000, no more, no less when they attain age 25. Any income and any appreciation arsing in the meantime belongs to the residuary beneficiaries. It is not unusual to see £1,000 set aside, perhaps in National Savings Certificates which are then encashed following A’s 25th birthday and the full amount paid over.
Rarely in the above situation do the residuary beneficiaries raise comment, probably as it seems to them to have been the deceased’s expectation and they know no better.
If it is intended that, on their 25th birthday, A receives £1,000 and the intermediate income - unless the £1,000 is invested in a non-appreciating asset (such as a bank account) how is the income to be allocated between the £1,000 to which A is entitled and the excess representing the appreciation to which the residuary beneficiaries are entitled?
In general, where it is intended the contingent entitlement includes interest it also carries any appreciation either by specific words or by being directed to be set aside (e.g. I give the sum of £1,000 to my trustees to be paid to A if and when he attains the age of 25 years).
The form of wording suggested by Susanne Jones would cover the situation where the legacy is held in a non-appreciating form but, as indicated above, may raise questions if the legacy is invested otherwise.
I agree with Simon and Malcolm that unless the testator is adamant that the legacies be paid only once the grandchildren have attained age 25, it would seem preferable for them to be absolute from the start. However, if the legacies were to be much more than £1,000 the issue of putting too much money in the hands of someone as young as 18 becomes a significant consideration as will the question of the entitlement to any intermediate income and appreciation. A legacy at 18 can also adversely impact any means tested benefits or grants to which the beneficiary might otherwise be entitled to.