There is no precise recipe, but it is said that a knickerbocker glory was first described in the 1930s. As well as layers of ice cream, jelly, fruit and cream it can be topped with different kinds of syrup, nuts, whipped cream and often a cherry. More complicated variations can sometimes include layers of things like meringue, or be topped off with a wafer.
It is so called because of its horizontal stripes, traditionally red and white, resemble stockings called knickerbockers.
The Knickerbocker glory photographed (above) was from a tea shop (note the decor and my tea cup in the background) in Richmond, North Yorkshire. This particular one sustained me during my Coast to Coast walk at the end of day 10.