Blimey!
He didn't hang around after Sarah Ann died then, did he?

I don't know if this helps you at all, but I did a little timeline in order to get my head around it all!
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1829 Matilda LAWRENCE born
1832 Charlotte LAWRENCE = Charles DERRETT
1847 Cornelius b Ch K, s/o Matilda LAWRENCE and ?, informant Charlotte DERRETT (nee LAWRENCE)
1851 Cornelius DERRETT with Charlotte, 41, her daus Matilda etc
1861 Cornelius with Matilda DERRETT unmarr head "grandson" - but Charlotte is absent
1864 Clara Matilda HERBERT born 13 White Hart St, d/o William HERBERT & Ann HERBERT formerly DERRETT
1869 Cornelius = Sarah Ann COMPTON, s/o William LAURENCE
1871 census married to Sarah Ann
1881 census married to Sarah Ann
1891 census married to Sarah Ann
1899 death of Sarah Ann
1899 marries Eliza PEARCE, s/o George LAWRENCE, miller
1901 census (have we got this??)
1903 Clara HERBERT death
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Have you looked for William and/ or George LAWRENCE on earlier censuses? It could be that he did exist in the background somewhere? Did we ever discover what happened to Matilda? If you have a spare day or so (!) you could try the full marriage/ death indexes which are currently free to view.
Arranroots
