The normal way of discovering a man's regiment from a census entry is to look for the names of the officers. You can then look them up in the Army Lists. Unfortunately this section seems to be incomplete. Normally officers are listed at the start of the return - but not apparently in this case. If you go to page 12 it says that page 13 is later on, but although this is listed as Camp 1, there does not appear to be Camps 2 and 3 etc.
I suggest you post a question on the Essex section asking if anyone had the 1881 census on CD. It may be a problem with Ancestry, or it may be that the returns for Camps 2, 3 etc have been lost.
If you can get to Kew you can see if his papers have survived. Also, by looking at the places were children of other soldiers were born you may be able to identify the regiment from these. I see one (aged 3) on page 1 was born in the Cape. I will dig out an Army list from c1877 and see which regiments were in southern Africa at the time. You could also buy the birth certificate of his son. This may give the father’s the regiment.
The only way to discover his regimental number is from the man’s service record or the Muster Rolls in Kew.
Ken
