tl;dr: don't do it!
The weather was near-perfect today, so I decided to cycle to work rather than take the horrible tube. I grabbed my stuff and set off, intending to drive leisurely and find my way to work when reaching central London. The road is pretty much straight up until the very last bit so navigation wasn't too difficult. My route takes from Ealing to the Victoria, either via Shepherd's Bush or Hammersmith. Either route is about 14km. I tried both today.
Finding the right way in London is not very difficult. Actually getting on the right way is fucking impossible. Some of the square roundabouts have such a weird get-in-lane system that its flat-out dangerous to even try and get in the right lane on a bicycle. Hesitate for a split second and you lose your spot and you're surrounded by cars that are actively trying to kill you. I exaggerate a bit, and my exaggeration wrongfully makes the alternative seem like a viable option. Instead of driving on the road for these crossings, you could theoretically take the sidewalk instead. The problem is time: staying on the road takes 5 seconds to cross, driving up and down stupid pedestrian tunnels takes 5 minutes.
Some colleagues of mine who enjoy cycling have told me they quite like driving in central London, or that "it's not so bad". It is. London is just not meant for bicycles. I've been around central London by car (as a passenger) many times. I've observed other drivers' behaviour. It's far from perfect and sometimes downright dodgy, when in a car. On a bicycle those cars turn into kamikaze pilots trying their very best to get you off the road. I can't tell how many times I've been cut off at roundabouts or even just on a straight road. London cars don't know how to deal with bicycles.
I have to mention the road quality. Because it's not very good. There's bumps and holes everywhere. When you're at speed and see a hole coming up you can sometimes swerve, but usually you have to brake massively because the driver behind you is making it clear that he won't tolerate you taking up another centimeter of road. Also, there's glass everywhere.
Then there's the buses that pass you and then stop 5 meters in front of you to let passengers out. Passing the bus on a bicycle is yet another lifethreatening experience because the drivers behind you won't look ahead to see you changing lane. If you do manage to survive then the entire process repeats itself 1 minute later.
I could live with any one of these nuisances (except perhaps the many-many-bus problem), but all put together it's just right there at the border of being enjoyable/unenjoyable. And I mean right at the border. At some stretches it's really great to make progress at speed, but then junctions and buses and traffic jams (that leave no space for bicycles to pass) happen just a little but too often for comfort.
Consider the alternative: taking the tube. It takes about 2/3rds of the time, could be boiling hot and packed full of people, and costs money. I am a lazy person by nature. That is why I know that I can't allocate a lot of my free time to exercise, because I simply won't do it. But replacing an already annoying commute by something almost equally as annoying, yet providing exercise, that might be something to consider.
If only it didn't always rain in London...