I am about to create a US will as a dual UK/US citizen, tax resident in the USA. My interpretation of the recent changes in UK Inheritance tax is that provided one remains non-tax resident in the UK, only UK assets will be taxed by HMRC. I have a will in the UK for UK assets. Therefore, i should be able to talk to a lawyer in the US to draw up a will for my US assets without them being on top of the UK inheritance tax situation ie a regular lawyer from my state. I ask because i thought that the wording on the US will that put everything in trust used to have to be carefully worded to avoid UK inheritance tax and therefore needed the input of a (seemingly difficult to find) lawyer in the US that was also familiar with UK inheritance tax. Is this correct?

Ok, so after listening to episode 43 of 'We're the Brits in America' (thanks for the recommendation Alan 17), as a dual UK/US citizen > 10yrs tax resident in USA with kids and wife also in USA and no (current) intentions for anyone to move back to UK, i am reasonably sure that i can just create a US will as a regular US citizen. If that changes, then we would need to take expert advice but would have 10yrs to sort that out. So UK property and SIPP would be subject to UK IHT (and £325K nil-rate band), US assets subject to US estate tax (with a considerably higher effective nil-rate band)

There is actually no 'US Will'. Each state requires its own legal will. So if you draft a will in your present state of residence and then move to another state, you will need to draft a new one. Check also if your state applies its own estate tax in addition to the federal tax. Also, in a very few cases states have an inheritance tax for the recipients of the estate (this might have changed in the past few years, but worth checking).

That is objectively not true. While it makes good sense to review and update your will if you move to another state, not least because rules on executors and probate can vary between states, it isn't something you need to rush off to see a lawyer about the day after you move to another state.

More generally, there are two opposing views on signing different wills in different countries. Some people argue it simplifies the execution of the will, others argue that having two wills is both unnecessary and can cause confusion, or even conflict as you can, objectively only have one last will and testament. And to be clear, it is perfectly possible, and far from unusual for a will written in another country to be endorsed by the probate court in the UK for the disposal of assets the decedent left in the UK; also having a foreign will translated for the purpose of probate in the UK is not unusual either.

So if there is more than one will, there is the potential for the remainderman (the one who gets "everything else") in the later will has a potentially good case to challenge any earlier will(s) written in other country(ies). If you only have one heir, the issue would be moot, but don't underestimate the potential for two or more heirs to get into a legal dispute if you leave more than one "last will and testament". .... Proceed with caution!