Each index entry comprises basic naturalisation certificate details, which vary by date, by the archive record series and by the type of naturalisation certificate issued. However, the records usually include a combination of the following information:
Age or date of birth
Names of parents, or spouse and children, if applicable
Place of origin and original nationality
Naturalisation certificate date and number
These records are abstracted from archive record series HO 334 and HO 409 held at The National Archives in Kew. Series HO 334 contains naturalisation certificates (rather than case papers), while HO 409 is certificate index entries. HO 334 stops in summer 1969, as at that point official government procedure was no longer to retain naturalisation certificates but merely to maintain the index of certificates issued (as per HO 409).
Naturalisation certificates were issued to those who became naturalised British subjects, as proof of their status. These certificates contain a summary of key information submitted and evidenced during the naturalisation process – i.e. name(s) including aliases; age or date of birth and place of origin; residence; occupation; names of parents, spouse and any dependent children as applicable; and previous nationality. The index to naturalisation certificates gives briefer details.
It is important to understand that many foreign nationals settling in Britain throughout this period became permanent residents without becoming legally naturalised. As a general rule, it is probably true to say that the earlier a person arrived in the country the less likely they were to naturalise. For example, an individual arriving in 1850 was probably less likely to become a naturalised British subject than one arriving in 1950. Naturalisation is a formal process requiring interaction with authorities, significant paperwork and expense, and many people either were not aware of the process, or did not feel the need, or preferred not to (for any numbers of reasons, from suspicion of authorities to attachment to their birth nationality). Again to generalise, those pursuing middle class occupations and professions were probably more likely to take the route of naturalisation than those among the working classes.