The busts were commisioned by the Towneley sub-committee as replacements after they had rejected two busts commissioned from Alfred Gilbert, which had been arranged by Walter Gilbert. Eventually the sub-committee relented and purchased the rejected work by Alfred Gilbert.
Letters between Walter Gilbert and the sub-committee relating to the commission have survived and can be found in the history files. A more detailed account of the commission is available as a pdf from www.atoz.myzen.co.uk/museum/downloads .
For a detailed account of Walter Gilbert's work see an entry in Wikipedia.