Found a possible mother:

London, England, Marriages and Banns, 1754-1921 about John Harmsworth
Name: John Harmsworth
Spouse Name: Harriet Plumeridge
Record Type: Marriage
Event Date: 30 May 1836
Parish: Lambeth St John the Evangelist
Borough: Lambeth
Register Type: Parish Register

John and Harriet appear in the 1841 and 1851 Census with a George