Why would Lloyds Bank want a form W8-BEN?

I've had British citizenship for over 10 years. I renounced my US citizenship last year. A couple months ago I received FATCA related letters from two of my banks, Lloyds and Santander. The Santander letter basically said "we think you might be a US citizen. If you are, give us your SSN, if you're not send a certified copy of your renunciation document". I sent the copy of the renunciation document and got a letter back saying all was fine.

Lloyds have been much more of a struggle. First they send a W-9 form and say "fill this out". I sent a letter back with a copy of my renunciation form saying that I'm not a US citizen so it doesn't apply to me. Next I get a letter back asking for proof of UK citizenship so I send a copy of my passport. Now they are asking for a W8-BEN form.

My question is why do they need this? I'm not a US citizen, I have no US income, I can't work out how the form applies to me.

I won't get worked up about it.  I would simply fill out the form and be done. It is easy to do and no skin off your nose. It gives you the chance to attest to the fact you are not a US citizen, since a W-8BEN form is not to be completed by a USC.

Lloyds will not be sending this form to the IRS. They simply keep it in their own records. If you were to open a Lloyds share dealing account and invest in any US companies the completion of the W-8BEN would enable you to receive US company dividends with only 15% US withholding tax taken off.

Send them the CLN & the W-8BEN & ask them in return to confirm that they will never ever report on you under FATCA.