Reporting US Income on a UK Tax Return

I'm wondering if there are any US citizens here who are resident in UK who have filed a UK tax return AND who have reported US earned income on that UK tax return?

I thought that if I wasn't employed in the UK and didn't have any bank accounts in the UK (earning interest) and no national insurance number that I wouldn't be required to file a UK tax return.  But I've been doing some reading that suggests that if I'm resident in UK, which I am because I have ILR, then I should be filing a UK tax return AND reporting any "foreign income" which would include any income generated from bank accounts and investments in USA. Just when I thought filing a US tax return from the UK was complicated enough, it becomes even more so as I'm wondering if I should be filing a tax return for the UK as well?  

What I can't seem to find out is:  If I am required to file a UK tax return, is there a certain amount that you can earn abroad before it has to be reported to the UK and what amount would that be?  

Are you doing this work in the UK? Have you thought about National Insurance?

You might want to have a look at this HMRC document, which defines residence and discusses filing tax on a remittance basis or a worldwide basis.

http://www.hmrc.gov.uk/cnr/hmrc6.pdf

Are you doing this work in the UK? Have you thought about National Insurance?

No, I'm not currently employed anywhere but only maintain bank accounts and investments in USA.

You might want to have a look at this HMRC document, which defines residence and discusses filing tax on a remittance basis or a worldwide basishttp://www.hmrc.gov.uk/cnr/hmrc6.pdf

83 pages of words and flow charts?  That's freakin' unbelievable dude! My head is now completely done in!
              . . .  and I thought it was a simple question I asked. 

Here's 5 pages to read.

The answer to your question is in the 5 pages.

http://www.hmrc.gov.uk/international/residence.htm

http://www.hmrc.gov.uk/incometax/tax-arrive-uk.htm

http://www.hmrc.gov.uk/taxon/foreign.htm

http://www.hmrc.gov.uk/sa/need-tax-return.htm

https://www.gov.uk/income-tax-rates