7. The War Machines
The first real present day story set on Earth and it's amazing that the series took three years to make that happen. The War Machines gives us a glimpse of what would be to come and shows that the series doesn't need to be historical or ultra-science fiction as it had been up until that point. This is a mostly appreciated story yet it never appears in any top story lists, possibly because of the disappointing exit of Dodo half way through. However we do also gain Polly and Ben, one of my favourite companion pairings.