Britain was increasingly preparing for war throughout the whole of the year from September 1938, and many fanciers were forced to abandon breeding budgerigars throughout this difficult period.
The hen of the pair was obtained from Mrs Codner of Torquay and was a "muddy colour, half way between a Cobalt and a Mauve."
All the young from this pair over two seasons were Cobalts, with one exception: a grey cock with black flights and tail feathers.
A grey mutation, believed to have a recessive action, appeared in the aviaries of Peter Bergman, of Sydney in 1992.
A further grey mutation, the anthracite, appeared in Germany in 1998 in the aviaries of Hans Lenk, who successfully established the strain.
A single anthracite factor has a similar effect to the Dark mutation, causing a Skyblue to become Cobalt in appearance - as was suspected with the English Grey (see Genetics below).
The description is virtually identical, and the cobalt appearance of a Skyblue with a single anthracite factor is exactly what was suspected for the English Grey.
Due to the similar appearance of the English and Dominant Greys they were first thought to be the same variety, although the reported breeding results showed clearly that Mrs Harrison's birds were the result of a simple dominant gene whereas Mr Brooks' Greys could not be so easily explained.
Mr Brooks published clear and detailed breeding records of all his English Grey pairings between 1933 and 1938 in the Budgerigar Bulletin.
Dr Daniels states that this hypothesis satisfactorily explains all the breeding results reported by Mr Brooks, including the lack of Mauves.