The remainder will be treated like any other gift into trust (a chargeable transfer (CT) in the case of a discretionary trust, or a potentially exempt transfer (PET) for a bare trust), leaving the IHT net after 7 years (or 14 years in some cases).
What's left over will be treated similarly to any other gift placed into trust (considering it a chargeable transfer if it's a discretionary trust, or a potentially exempt transfer if it's a bare trust), resulting in IHT after 7 years (or 14 years in certain cases).