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).
The leftover will be handled like any other present into trust (a chargeable transfer for discretionary trusts, or a potentially exempt transfer for bare trusts), leading to IHT after 7 years (or 14 years in specific cases).