Hi,
Welcome to Rootschat

There is a John Walker Alcock registered AMJ 1842 Banbury (includes Sibford Gower)
The Gro gives his mmn as Callow
The following is all supposition and would need to be looked at more carefully
Closest I can find for a marriage...from Familysearch 1835 Epwell for a John Alcock and Mary Callow
Perhaps John snr died and Mary remarried a Moses
There is a marriage 27th April 1846 Tunstall, Staffs
Moses Hancock and Mary Ann Alcock parents Joseph Hancock and Samuel Alcock.
Perhaps John died and John jnr only knew Moses as his father.
As I say, perhaps a flight of fancy on my part

When do you fist find him in the censuses?
Cathy