Treaty torture

We are perplexed by the US/UK estate tax treaty specifically Article 4(1)(a) which defines when an individual is domiciled in the US (for estate tax purposes).

Our first query is the difference between US resident domiciliary and national. We understand that for these purposes “national” is synonymous with “citizen”.

We also understand that “domiciliary” is a subjective US assessment of the connection between the US and the individual after considering wills written intentions location of residences citizenship etc. But within the confines of Article 4(1)(a) what does “resident” mean?

The commentary we have read makes the clear point that residency for US estate tax domestic rules is measured by domicile and we assume that means the subjective domiciliary test above.

But when the treaty mentions “resident” in Article 4(1)(a) does this mean “satisfies the domiciliary test” (which we mention...