One of the most widely disseminated and greatly varied of the recently-made morris dances is "Lass of Richmond Hill". Its origin and subsequent history are not as well known as they could be, and some of what is "known" turns out not to be true.
The dance was composed circa 1970 by Martin Johnson of Hammersmith Morris. The Hammersmith origin is confirmed by Roy Dommett, Rob Williams, Nick Robertshaw, and others. While authorship has been attributed to Jim Reynolds and John Kirkpatrick, Williams, who says he was present at the dance's birth, states that Johnson wrote it sometime in 1970-71. Ian Dedic says he met an ex-Hammersmith member (name unknown) who confirms that Johnson was the author, but gives the date as 1969. Gordon Potts reports Johnson confirms he wrote it.
Hammersmith danced it (and still does) as a Longborough dance with five choruses. Dedic's source says Whiteknights Morris (the Reading University student's team, possibly long extinct) simultaneously learned it as a Bledington dance, but that only the Longborough version survived for long and it was probably the version all other extant ones derive from. (Colin Egan says Johnson may have taught it to the Whiteknights first, then Hammersmith.) Dommett gives the Hammersmith original version along with several adaptations in a document included in "Roy Dommett's Morris Notes" (edited by Tony Barrand, available through CDSS). These include several Fieldtown versions, a Bledington version, and a Badby version.
Subsequent meanderings through the maze of twisty little passages that is 20th century morris provide intriguing reading. A Fieldtown version by Judy Erickson of Muddy River Morris was based on one or more versions known by Cynthia Whear (of Marlboro, etc.), who herself had done a Withington adaptation. It appears that Whear's versions came from the Badby version taught by Tim Cavanaugh of the Marlboro Morris Men (who later performed an Old Spot Longborough version); Cavanaugh learned it at Pinewoods from Jenny Joyce of Windsor. Meanwhile the Black Jokers apparently got their (three chorus) Longborough version by adapting a Fieldtown version danced by East Suffolk. It's likely that East Suffolk's version came fairly directly from Hammersmith's.
And so on.
Just to complicate the story further, Ian E.D. Carter reports that Angel Morris of Islington independently invented a stick dance in their own style (roughly Fieldtown) to the tune in about 1978 or so, called Lass of Pentonville (a local place name).