2008-04-02 BBC NEWS | Entertainment | Who actors launch fourth series BBC NEWS | Entertainment | Who actors launch fourth serieshttp://news.bbc.co.uk/2/hi/entertainm...The first episode of Series Four sees them reunited unexpectedly The second saw the pair transported to ancient Pompeii on the eve of Mount Vesuvius's eruption - impressively rendered in a computer-generated sequence Tennant called "gob-smacking".