How far can you see big ben from?

The Houses of Parliament, which include the Elizabeth Tower (commonly and incorrectly called Big Ben) are located in central London. From there, you can see for many kilometres in all directions, depending on the weather and pollution. On a clear day, it is possible to see as far as the Chiltern Hills, which are about 40 kilometres to the northwest, or even the North Downs, which are about 60 kilometres to the south.