Any time left on your old passport when you apply will be added to your new passport, up to a maximum of nine months.

Not only is a passport essential but you also need to make sure that it's valid for at least six months beyond the end of your trip - Cambodian immigration will not issue a visa if you have less than six months' validity left on your passport.

Check the entry requirements of the country you intend to visit well in advance - some require that you have a certain amount of validity left on your passport when you travel, so you may have to apply for a new passport in time for your trip.

Certain countries require you to have a minimum period of time left on your passport when you arrive.

A dual national child entering Egypt on a foreign passport is able to leave the country on their Egyptian passport.

Some countries may require a passport to be valid for a certain period after entry, eg to enter Turkey you must have six months left on your passport.