I started cycling last March and haven?t looked back. I used to work by London Bridge, but now work by Liverpool Street. I cross via Tower Bridge (via Surrey Canal). Although it is closer to cross via London Bridge, there are so many pedestrians (that I think we can agree all cyclist dread), that I find that rout safer. A great Website to check out is http://www.gmap-pedometer.com/ . You can calculate the lenght of your route