If you start from the beginning, the real beginning you will need to spend a long time watching because it started in 1963. Difficult to say really. You could start with the series starring Christopher Ecclestone, which was the first of the new series of Doctor Who, after a break of many years, then David Tennant's Doctor and finally the present Doctor, Matt Smith.
Maybe once you've got up-to-date you could then go back to the start of the old Doctor Who, I think you can get them on DVD.

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Don't make people into heroes John. Heroes don't exist and if they did I wouldn't be one of them.
