Census night 1871 was April 2nd.
You have all the details I could find on the 1851 census. Because this James was not with his regiment, the census does not show which regiment he was in and I don't know whether the 61st was stationed at Chatham in 1851. This James was a private not a sergeant. He would have to have had a meteoric rise to have made sergeant by 1853. However men did rise and fall in the ranks, courtmartialled for things like drunkeness and if he had previously made sergeant he could have quickly returned to that rank again or he could indeed have been an exceptional soldier.
As you know your James' regiment and that he did receive a pension, it will be perfectly possible to find his army attestation papers at The National Archives, which would give you more details about him. You could also follow him through the quarterly muster rolls for the 61st.
I would read the research guides that the National Archives supply on their website before your visit.
http://www.catalogue.nationalarchives.gov.uk/RdLeaflet.asp?sLeafletID=14http://www.catalogue.nationalarchives.gov.uk/RdLeaflet.asp?sLeafletID=16http://www.catalogue.nationalarchives.gov.uk/RdLeaflet.asp?sLeafletID=15The help desks at The National Archives are staffed by very informative and helpful people but obviously if you know what you are looking for, you will be able to help them to help you and so you will get the most out of your visit.
The army wasn't fussy about the age of men who enlisted or much else about them. Men were frequently a little vague about their age and boys would just adjust their age up a little. The army was not in the habit of asking questions. If your James enlisted as early as 1840 (when he could have been as old as 25) then by 1861 he would have served 21 years and be eligible for pension.
If James was in India then other children could have been born and possibly died in India (have you looked in the overseas births?). If he was indeed in India then he would have been there through the Indian Mutiny 1857-1858. His attestation papers and the muster rolls together will tell you where he was stationed - in the case of the muster rolls every quarter each year.
This website gives an extremely detailed account of the 61st in India through the time of the mutiny listing the names of casualties (James does not seem to be mentioned)
http://members.tripod.com/~Glosters/index-4.htmlThe website says the 61st left India in July 1860. In which case the whole regiment should have been in England for the 1861 census and James earlier if you have a birth in this country for one of his children in 1859.
You don't give any details about James' wife and children, so I can't really help search for them on the 1861 census without some further information.
Regards
Valda