Transferable nil rate band & more than one spouse

The new transferable nil rate band provisions apply so that part of a spouses unused nil rate band on death can be used on the death of their surviving spouse. If a survivor has remarried after they were widowed and were unfortunate enough to be widowed again how does this impact on the amount of the nil rate band used? It's important to understand how the transferable nil rate band works. The legislation applies a percentage basis. ie the surviving spouses nil rate band is increased by a given percentage according to the deceased spoused unused nil rate band (ie unused nil rate band/nil rate band * 100). This cannot exceed 100%, so even if there were two deceased spouses that had the full nil rate band available, the additional nil rate band for the surviving spouse would still only be 100% of their nil rate band.