There are no whales that live in the River Thames, which flows through London. However, there are some whale-watching tours that depart from the city and take passengers out into the North Sea, where they can see minke whales, porpoises, and other marine life.
The distance between London and the nearest whales varies depending on the time of year and the location of the whales. In general, the best time to see whales in the North Sea is between May and September, when they come to feed in the nutrient-rich waters. During this time, it is possible to see whales within a few miles of the coast.
However, it is important to note that whale watching is a unpredictable and there is no guarantee that you will see any whales. If you are planning a whale-watching tour, it is a good idea to do some research in advance to find the best time and place to go.