It then proceeds north to make a confluence with a secondary stream, also called Tykes Water, near Kendal Hall Farm.
A minor tributary collects water from farmland north of Borehamwood and also joins near Kendal Hall Farm.
Kitwells Brook joins the main stream just north of Radlett and drains land to the east in the direction of Shenley.
Tykes Water Bridge in Aldenham Country Park features in the opening credits of the Peter Cushing and Christopher Lee film, Dracula A.D. 1972, and is used in several episodes of the Diana Rigg and Linda Thorson series of The Avengers .
Earlier, in 1966, it was used as the setting for the opening sequence of "The Saint" episode "Little Girl Lost" featuring Roger Moore.