As the name Legbar implies, Barred Leghorn, or Brown Leghorn x Barred Rock (To create the autosexing production type bird) according to the history I know. Throw in British Araucana to get the crest and blue eggs, as I understand it, so we are no longer a Legbar, technically. It's now an autosexing crested blue egglayer, far removed from a Leghorn, or Barred Leghorn for that matter. Just because the UK SOP adopted it as the "Crested Cream" Legbar, doesn't necessarily mean that's what it is and should be.
Legbar, by definition, is a Barred Leghorn, as Punnett intended it to be. See the following.
Quote: He made numerous crosses made between Barred Plymouth Rocks, which in the interwar period was a very popular utility egg laying breed. (Our modern egg-laying hybrids had yet to be developed.)
in 1943 the Autosexing Breeds Association was formed and various breeds developed - each breed was named according to its cross, but ending in "bar" from the barred feather parent
Brussbar from the Brown Sussex
Cambar from the Campine
Dorbar from the Dorking
Legbar from the Leghorn
Marbar from the Marans
Welbar from the Welsummer and so on.
Around 1932 the Legbar was the second of these breeds to be created at Cambridge Agricultural Research Department They were from a Brown Leghorn cock (gold sex linked) crossed with a Barred Plymouth Rock hen (silver sex linked) From this cross any progeny without barring were discarded, the remaining were selected for Leghorn type and mated together.
The pale coloured males (carrying two barred genes) and the crele coloured females were kept, and all dark (crele) male chicks were discarded. In order to increase numbers and bloodlines these Gold Legbar males could be crossed back to brown Leghorn females, and from this cross half produced dark crele males which again were culled.