ok let's face it, unless they've lived in a City or even London itself (in the past), parents in London DO NOT COMPUTE.
I took my mum and step dad on a river trip and my stepdad asked my which bridge was 'knightsbridge'. they talked to people on the tube. They had lunch TWICE on the concourse of Euston station as it was 'convenient to their hotel'. They thought that you couldn't take luggage on the tube.
Am I just impatient or do parents just like to go against the grain and annoy you for the sake of it?