Full details of HMRCs view on domicile can be found in their booklet IR20 (
http://www.hmrc.gov.uk/pdfs/ir20.pdf).
In detail:
1. amarylis may have a domicile of origin in T & T, but this depends on whether or not your father was permanently settled there when you were born. More info would be needed. This domicile of origin may have been supplanted by a domicile within the United States if father settled permanently in a US state by the time you were 16 years old.
The UK law (case law going back to the 14th century since the UK has an unwritten constitution) says that domicile follows the father if the parents are married; but follows mother if parents are not married or father is not known.
No-one is domiciled in the US or the UK. Rather they are domiciled WITHIN each place. In terms of the UK it will be in England & Wales, Scotland or Northern Ireland and in the US in one of the 50 States. This is because one is domiciled in a place that has a seperate body of law.
2. Quarter-gill may still be domiciled outside of the UK if you expect to leave on retirement, completion of work, completion of childrens education, death of spouse or some other event. There are plenty of folks who have lived here for 20 to 50 years plus, who are still domiciled outside of the UK because they still consider somewhere else as "home".
3. Geetak may have a domicile of origin in India if father had not settled permanently elsewhere by the time you were born. If father settled permanently somewhere else (eg in a US State) by the time you were 16 then you may have a domicile of dependency elsewhere.
So the trick here is BANK OFFSHORE, claim non-UK domicile and don't bring offshore interest income to the UK. This is a standard practice for expats coming to the UK. Jersey, Guernsey & the Isle of Man are offshore for UK tax purposes but part of the British bank clearing system, so this is real easy in practice.
For anyone who expects to be here for only 2 or 3 years and will have non-UK workdays this technique will also save taxes on employment income too...