Readers' forum : Domicile decision

My client is a US citizen but has been a long-term resident of the UK for many years. She comes within all the rules relating to deemed domiciles for inheritance tax and suchlike. The client is now considering whether to apply for a UK passport but she will not seek to renounce her US citizenship. As far as I am aware none of her other circumstances will change as a consequence.

Would HMRC consider that the application for a UK passport is strong evidence of the client having acquired a domicile of choice in the UK?

Further are there any beneficial or detrimental tax aspects of becoming UK domiciled in fact rather than simply being treated as having a deemed domicile?

It would be good to have such information to hand so that I can advise the client on whether proceeding with the citizenship application would...