Hi,
Could it be a second marriage for Ann, her maiden name would still be shown on the birth certificate of children from her second marriage.
In 1851 I can see Isaac WALKER with his widowed daughter Ann,
1851 HO107/2144 f.536 p.24 Belper
No. 21 Birkin Court
Isaac WALKER Head Widow 60 Retired Nail Maker Derbyshire Belper
Ann HUNT Daur Widow 28 Employed at Cotton Spinning Factory " "
William WRAGG Lodger Unm 39 " " " " " "
Jeremiah SMITH " " Unm 35 Framework Knitter Nottinghamshire
There is this marriage,
Ann WALKER Mar Q 1843 Belper v.19 p.327
Matthew HUNT (amongst other names)
If Nettle has sent you the image you can see Matthew HUNT was living in the same household as Isaac & Ann WALKER in 1841.
This could be Matthews death,
Matthew WALKER Mar Q 1845 Belper v.19 p.359
Then there is this marriage,
Ann HUNT Jun Q 1857 Derby v.7b p.599
(amongst other names) James ATTENBOROUGH
In 1861 I can see this family which seems to include your Isaac, transcribed as HATTERBOROUGH, I think it looks like HATTENBOROUGH
1861 RG9/2509 f.104 p.8 Belper
Short Row
James HATTENBOROUGH Head 40 Collier
Ann Wife 38 Mill Hand
Hannah Daur 8 Scholar
Ann Daur 3
Isaac Son 1
All born Belper.
This all seem to fit apart from you mention the oldest child was born 1843/4, I can't find any children born around then in 1851 except a John ATTENBURY, b.1847 who is the son of a widowed Mary Ann ATTENBURY, who to confuse things further is living at home with her parents, John and Ruth WALKER
Also where does daughter Hannah fit in
Now I've confused myself
Regards
Daisy