ID check for MLR

BIG WAL

I've been asked to advise a non UK resident to look at the mess he's got himself into with the balance sheet of a small UK registered company, which still has a small income. He used to live in the UK, but has been non UK resident for probably 2 years.

Question is how do I check his ID, as it's not possible to see his original passport, and he has no UK address.

Any suggestions will be appreciated.