I always thought it was "Clarke (comma) Hall and Morrison on Children", i.e. Messrs Clarke and Hall were two separate people. Indeed, that is how it is listed on Amazon. Wrong.
Whilst searching for nothing in particular this morning I came across the NSPCC history of child law in England and Wales 1884-1989 reading list. Amongst the list one discovers the history of this leading work on children law. It seems that it began with the snappily-titled: The law relating to children: a short treatise on the personal status of children, and the statutes that have been enacted for their protection by William Clarke Hall, published way back in 1894. That was followed by the second edition in 1905, with the equally catchy title of: The law relating to children: a short treatise on the personal status of children, including the complete text of "the Prevention of Cruelty to Children Act 1904" and all of the statutes relating to the protection of children.
In 1909 William was joined by one Arnold H. F. Pretty for the third edition. Pretty perhaps encouraged him to reduce the title to something more manageable, the simple: Law relating to children.
There then seems to have followed something of a lacuna. William (by then Sir William, I'm not sure when he was knighted) died in 1931 and the list make no mention of his famous treatise again until 1947 when Clarke Hall and Morrison's law relating to children and young persons: including the law of adoption by the eponymous A. C. L. Morrison and one L. G. Banwell was published, although strangely the list also refers to this as the third edition.
A sixth edition by the same authors was published in 1960 (not sure what happened to the intervening editions) and a seventh in 1967, by Banwell and J. R. Nichol, complete, for the first time, with a supplement. Clearly children law was expanding, as a second cumulative supplement to the seventh edition was published in 1970, with L. Goodman named as one of the authors.
An eighth edition, with L. Goodman taking over the reigns, was published in 1972 and, moving into my era, Margaret Booth (before she was appointed to the High Court) and Brian Harris edited the ninth edition, which was published in 1977.
The list makes no further mention of the work, before it ends in 1989. At some point it transposed into looseleaf, in which format (along with CD-Rom) it is now published by LexisNexis. Current editors include such luminaries as Baroness Hale, Mr Justice Ryder, Stephen Cobb QC and Professor Nigel Lowe.
As for Sir William Clarke Hall, he was a barrister but was known as 'The Children's Magistrate', for his work in the juvenile court. He devoted his life to the welfare of children, being involved in the reform of child law. According to this obituary of his son, he was instrumental in the founding of the NSPCC, bringing us full circle, although I can find no confirmation of this on the NSPCC website. He married the artist Edna Clarke Hall in 1898 and had two sons, Justin and Denis, the latter becoming a renowned architect.