"Mr Ancram is a man of many names and titles. You could, I suppose, call him Michael Kerr, since Kerr is his surname, but no one does. For many years, he was known by his courtesy title, Lord Ancram, but one day, at a big wedding where the butler was announcing the names of guests as they arrived, the young Michael murmured "Lord Ancram" in his ear and the butler, mishearing, shouted out, "MR NORMAN CRUM". Since then, Ancram has been known to his friends as Crum, and has preferred to be known to the public as Mr Ancram, which he isn't. He has been the Marquess of Lothian since 2004, but no one ever calls him that.
In addition, I see from Burke's Peerage, "Mr" Ancram is Earl of Lothian, Earl of Ancram ("(twice)", says Burke mysteriously), Viscount of Briene, Lord Jedburgh, Lord Ker of Newbattle, Lord Ker of Nisbet, Langnewton and Dolphinstoun, Lord Ker of Newbottle, Oxnam, Jedburgh, Dolphinstoun and Baron Ker of Kersheugh. He is married to the daughter of a duke. So was his brother, and two of his sisters are married to future dukes."
This is also the man who has been known to sing "The Streets of London" at Conservative Party parties.