The head of the household was asked to complete the details for each family
A genealogist's challenge under the Freedom of Information Act could unlock records providing a unique snapshot of UK families as World War II broke out.
These days someone who suddenly decides to research their family history can often make great progress over the course of an hour or two and without having to leave their home.
A huge amount of information relating to births, marriages and deaths is only a few mouse clicks away, provided by a variety of free and subscription sites.
Those in the UK who already know their link to grandparents or great-grandparents are particularly well served by published census details that reveal much about how our Victorian ancestors lived and worked.
But they are the lucky ones.
In today's society, where many family relationships are fragmented or obscure, those with a yearning to find out more about their forefathers often fall at the first hurdle, frustrated by the lack of accessible information relating to recent decades.
The publication of the 1911 census for England and Wales has helped many to establish their links and some of those with unanswered questions are hoping that the release of the 1921 census - currently expected in 2022 - will help them.
But that census release is set to be the last for a generation.
The 1931 census was destroyed in a fire and there was no survey taken in 1941 because of the war. It may be more than 40 years until the 1951 details become public.
"The truth is, it's often far more difficult to find out about recent history than Victorian history and beyond," says family historian Guy Etchells.
Mr Etchells is already something of a hero in the genealogy world, being credited as the driving force behind the early release of the 1911 census for England and Wales.
In 2006 he successfully challenged a decision by The National Archives to block the release of census details - a move that eventually saw the whole census going online earlier this year.
WHAT THE RECORDS INCLUDE
Occupation or employment
Military auxiliary or reserve forces membership
Now a similar appeal to the Information Commissioner under the Freedom of Information Act could unlock details from the 1939 National Registration of the UK - an emergency, census-like survey of the country at the beginning of the war.
"When authority is wrong, you've got to stand up to it, to improve the situation," says the 60-year-old, from Wakefield, West Yorkshire.
"I think it's vital. If I hadn't challenged the 1911 ruling you probably still wouldn't be able to get the 1911 census."
The commissioner has told the NHS Information Centre - which holds the 1939 details - that it should grant Mr Etchells' request for access to a record, previously withheld on data protection grounds, where the circumstances relate to people now dead - a stipulation Mr Etchells may yet challenge further.
The news has been greeted with great interest from probate researchers, the so-called "heir hunters", whose job it is to track down living relatives of those who left estates.
"None of the legislation forbids access to the records," says Mr Etchells.
"The records have been kept so that people can access them. They are not archived so that they can be hidden away.
"There's no point in charging people thousands of pounds a year to keep them if you are not allowed to access them."
The National Registration enumeration, carried out on the night of Friday 29 September 1939, led to the issue of about 46 million identity cards for citizens the following month.
Households were asked to provide information about the names, ages, sex, marital situation and jobs of those living there.
During the war, and until 1952, every civilian had to carry their card as proof of identity and address. The registration was also used as the basis for the issue of ration books for food and clothing.
TV genealogist and historian Nick Barratt says the development is "interesting", although he believes it is too early to say whether the challenge will "open the floodgates" to the publication of a 1939 database.
He says it could be a boon to people who are perhaps researching house history, as well as genealogists.
"The potential is huge, though - you aren't going to find any of this information on the 1931 or 1941 census," he says.
"There are massive gaps, particularly between 1939 and 1945 when there were no electoral lists."
The NHS Information Centre, which can appeal against the ruling, is "considering the implications" of the commissioner's decision.
Below is a selection of your comments.
The lack of two censuses makes the release of this information imperative. It amazes me how many people today do not know who their grandparents were and this data from 1939 would sit squarely on that period.
D. Hayward, Carisbrooke, Isle of Wight, England
Much data was collected in the past with a guarantee of confidentiality. Many people, including several frail and elderly members of my family, who are in the 1939 'census' are still alive and deserve to have their privacy respected.
Jennifer Foster, Salisbury
Definitely a good idea, the war ended 64 years ago, so most people involved in it will be dead, and the records released will be of great interest to people looking for records of their own families, as well as tracing their ancestors. This is a public record after all, and holding the information back from the public is in fact illegal.
Dr Harkins, London England
Since the NHS. are only being asked to release what is basic information, and not medical records, I fail to see what their objection could possibly be!
Anthony John Burns, Alva, Clackmannanshire
I would welcome the release of the wartime data as my late mother was a foreign national caught up in the UK at the start of WWII, hospitalised with appendicitis, unable to continue her emigration trip to the USA, and unable to return to her home in Sweden.
Peter Marton, Middlesbrough, UK
I am not convinced by the authorities arguments that the contents of any census should be withheld from public scrutiny. The contents of a census are available in numerous published lists such as Registry of births, deaths and marriage, electoral rolls, telephone directories, membership lists of professional institutes etc. albeit not in one comprehensive list as that of the census.
Peter J Lynch, Farnborough, Hants, UK
It is absolutely right to release this information. A great deal of money is going into private firms who transcribe these records into database files (with mixed accuracy). I assume the Government agencies charge them for the right to exclusivity and thereby raises revenue for the exchequer - badly needed right now. The records in question cannot be in any way contentious as the information is so basic.
Richard, Redhill, Surrey, UK
I have been researching my family tree and find the access to information that is 100 years old ridiculous, and I will be 80 years old before I can see the census from 1951!! I am trying to trace my father's family that he never knew, and because of this I am unlikely to be able to find a living relative. More power to people like Guy who are trying to change this.
LISA RICHARDSON, FARNBOROUGH
Considering that the current electoral lists are sold willy nilly I can't think of any real reason why such basic information couldn't be released except for the natural reluctance of government to provide value for money. Like the man says, we've been paying for them to keep this for years and years with absolutely no return - about time they justified their existence!
Andy Jones, Nantwich, UK