One cannot go to London and NOT SEE Westminster Abbey !  To do so would be a grand disservice to your trip. I mean how can you not experience the  most important (and heck, oldest) church in London :  site of coronations, burials, memorials, and lookalike to every Citadel in our dreams?! Yeah, I'm a big fan of this place. So big that I purposely and happily went here thrice in the two times that I've visited London! *  Taking the tube  to Westminster and  getting off Westminster Station , short and sweet!! While I greatly appreciated the presence of English all around (compared to everywhere else in Europe), I must say that  I found the Paris Metro to be more navigable compared to the London Tube . Must be because the Metro uses a numbering system (Get off the 6, Hop on the 9) compared to the system of the Tube which uses named lines (Jubilee Line... Jubilee Line.. Wait, what I am doing on the Metropolitan Line?!)