EXPAT FAQ
https://www.easyexpat.com/en/faq.htm
Do we have to pay UK taxes in the USA?
UK (like most countries) taxes you based on residency and not citizenship (like the US). Therefore, when you leave the UK, you will not be subject to UK tax (provided you keep your tax home outside of the UK for one full UK tax year, and do not come back to the UK for 91 days on average over 4 years).
You start paying UK tax as soon as you return to the UK to live and work.