James raises a good point, although it only applies if the IPDI is created using s.142 IHTA.
If the trust fund is appointed into the IPDI/flexible life interest trust (FLIT), using the powers in the will, s.144 IHTA applies. In which case s.142(4) has no application, and there is no similar provision applicable to s.144. Technically, the capital within the FLIT could be appointed away from the life tenant the next day. However, that could well raise questions from HMRC and lead to the arrangement being challenged.
Paul Saunders