My understanding is that Jill Rees' birds all trace their origins back to Jilly Potter. I need to get to know Jilly she probably could connect all the dots on information for another chapter of the CLB history from the 1990's to the present day. 
In 1988 the Cream Legbar was listed as one of the most critical of the auto-sexing breeds. Probably because it could not be out-crossed to the foundation breed to form new bloodlines like the Rhodebar, Wybar and other breeds could do. Sue & Shaun Hammon and David Applegarth were working with the CLB in 1988. I am guessing both of them out cross the CLB so I am guessing that there are at least two origins of the CLB now and possibly more since other have surely have outcrossed to leghorns, aracanas, etc. in the UK.

In 1988 the Cream Legbar was listed as one of the most critical of the auto-sexing breeds. Probably because it could not be out-crossed to the foundation breed to form new bloodlines like the Rhodebar, Wybar and other breeds could do. Sue & Shaun Hammon and David Applegarth were working with the CLB in 1988. I am guessing both of them out cross the CLB so I am guessing that there are at least two origins of the CLB now and possibly more since other have surely have outcrossed to leghorns, aracanas, etc. in the UK.