My Passport has Expired, How Do I Renew It?

All the info online refers to "renewing" you old passport and what to do if you look very different, etc etc etc.
Alternatively, it mentions your first passport.

There is no mention of what to do if your current passport has run out and is now well out of date.
Update: Stock: This Yahoo Answers UK!
Update 2: Dody: This is Yahoo Answers UK!
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