On Wed, 07 Nov 2007 00:41:22 -0800, Keith Raeburn wrote:

Myself and a friend will be in London for a day in a few weeks time, and
would like some advice on if, and which, travelcard we should buy.

We expect to make 3 or 4 Tube journeys in the central area.
Is it worthwhile getting a one day card, or just pay for individual
journeys?
Also, can they be bought in advance for a particular day?

Get a pre-pay Oyster card from the first Tube ticket office (not
machine) you arrive at,

This is overkill for tourists (unless they are really strapped for
cash). They should just get One Day Travelcards each day.