1. Use a compass or a smartphone app that shows the direction of Mecca.
2. Stand in a clear outdoor space where you have an unobstructed view of the sky.
3. Hold the compass or smartphone in front of you and align it with the direction indicated as "Mecca."
4. Adjust your position until the needle of the compass or the arrow on the app points towards Mecca.
5. Once you are facing the direction of Mecca, you can begin your prayers.
It's important to note that the exact direction of Mecca may vary slightly depending on your exact location in London, so it's always best to use a reliable compass or app to ensure accuracy.