Originally Posted by Greg66

A partial postscript. After a bit of a wait on the phone I spoke to a very helpful lady. She directed me to https://help.cbp.gov/s/questions.

Select Traveller Compliance I-94 and 10 day notification email from the drop down, and you have the opportunity to send a detailed explanation and to upload docs.

A request to BA for the manifest resulted in a pro-forma saying that could take up to 28 days. So for now I have submitted my passport (although as I have not left the UK since returning from NY, that will be of limited use), my e-boarding pass from my phone, and a credit card statement showing spend in NY over the days I was there and then solid retail spend in London. Plus I have offered to submit the manifest if and when I get it.

Now it's a case of wait and see.