Naturally, my first point of call is Transport for London, which has a nice route planner that works out routes across London for you. It includes walking routes, National Rail, the Tube, the River and a host of other options.
I wasn't entirely happy when I discovered that it was going to take an overground train, two tube trains and a bus 90 minutes to get to me to my destination.
Happily, Tom came to the rescue when he suggested travelling by car. Since public transport is generally so good in London, and the roads so busy, I haven't thought about driving anywhere that wasn't well away from the City since I moved here. That is something I'm going to have to change as the road route is supposed to take just half an hour.
…although it does go along the Great North Circular so I'll be praying that it doesn't get horrifically busy until later in the day.