As esprit says, you will need it if you look under 30 (or if the clerk isn't sure or just wants a laugh at your passport photo )

Even if you go to a bar and you are not wanting to drink alchohol, they may still ask you for ID.

Carry ID with you at all times. I used to hate carrying the passport around with us, but you have to do it.

Do you not have the option to have a driving licence with photo on it in the UK now? Too late to get one for the 17th Dec, but may help someone else.

Also some stores may ask to see ID even when you make a purchase with your credit card.

--Kay