Alfred (Comte) is noted in this same source as having been "de Morton" but his mother was Amélie Baysselance, with her mother being in turn a Carrière and there is no Morton to be had "...not even for ready money Sir" (sorry Oscar, but I have always adored that line.) So maybe it is another generation back, but there are Manchon, Thibault, Pommart, Pavard, Boileau, Bruslin, Beaulieu, Rateau de la Noue and a dozen more equally damscene noms-de-famille, sufficient to keep a Francophile drooling until the ambulance arrives, but no Morton.
So d'ou vient-il ce 'de Morton'? Maybe it did come from Creed Royal and the "de Morton" was retro-appended to the biographical sources via relatives given to romantic embellishment. Creed Royal is mentioned in several Manchester papers but only as a flautist (by the way, he married twice, secondly in Melbourne but I can't go spending more money on certificates) and only in one source is he called a Colonel. His daughter Kate of course, became the Countess and his other daughter Miss E. Royal (can't find out her first name, though I did note it years back on a web page that has now vanished) married Tom Fawcett the actor then Dan Briggs O'Hara the comedian before dying the same year (1876) as her father, he in Melbourne, she in Rockhampton. Kate didn't last out the decade either. She died in Paris in 1872 I think it was. Someone certainly made the monkey angry in that family. Tom Fawcett did leave behind though, one child, though what became of it I do not know.
"Morton, d'ou viens-tu?"