The River Colne, and its sister river the Colne Brook, arise at North Mymms Park in Hertfordshire and then flow westwards and finally southwards along the water course known as the Colne Valley in the north west Home Counties. They often form the county boundary for Hertfordshire or Middlesex as they make their way towards the Thames.
The Colne tends to split into two as it wends its way downstream and the split off is called the Colne Brook. The rivers eventually part company and end up in the Thames near Staines.
Rivers Colne and Colne Brook fishing venues.
From upstream to downstream: