Indeed you need a passport, I looked into this before when I went to Prague (Couldnt find my passport till last minute)
In fact that reminds me, where is my passport, I havent seen it in a few months. Better take a look when I get back to the flat and it has my visa in it
![Sad :(](http://www.tekforums.net/Smileys/teksmileys/sad.gif)
I think you can still get same day service for passports in London, Euston station has a place if i remember correctly