On 2 March 1944, General Francisco Franco's government passed a law to issue all Spanish citizens with a personal identification number (DNI).
The Council of Ministers approved the introduction nationwide for "total efficiency for the unquestionable accreditation of the individual".
A public competition was held to design the first DNI and it was won by Aquilino Riusset Planchón who was awarded a prize of 30,000 pesetas. The rules of the competition were that the document had to fit inside a wallet, have enough space for the required text, a fingerprint and a photograph and ink that could not be altered by light.
Although the law was passed in 1944, it wasn't until 1951 that the first document was issued, with fingerprints as well as parentage and address.
General Franco himself was given the first ever DNI, with the number one, and his wife, Carmen Polo, and daughter, Carmen Franco, were issued with numbers two and three respectively. Number 10 to 99 were reserved for members of the royal family.
Since the issuing of the first DNI, the documents have evolved along with technology. Until 1981, they included a box which determined the owner's profession.
In 2004 a pilot project was launched by the Spanish ministry of the interior with a view to introducing electronic DNI cards. The cards would contain the owner's digital signature and photograph, using facial imaging technology. A chip would hold other information, including a digital fingerprint.
In 2006 the first electronic, laminated national identification card was issued in Burgos and was the same size as the current EU driving licence.
All Spaniards are issued with an eight-digit number and a control letter, which stays the same throughout the person's life.
The format remains largely unchanged today, although the fingerprint is no longer part of the data.
Like a passport, the card must be renewed every 10 years at a national police station.
DNI numbers can be used for identification in all situations, from going to the bank, to buying houses and travelling within the European Economic Area (EEA) and some other countries. The DNI number is also used for issuing Spanish driving licences.
It is legal requirement to have a DNI from the age of 14 and to produce it when required to do so by an officer of the law or face a hefty fine. Nevertheless being asked by the police to show ID for no reason is uncommon, unless it is a routine part of an incident or when another offence has been committed, such as speeding.
To apply for DNI, it is necessary to have Spanish nationality. The equivalent number for foreigners is the NIE (Número de Identificación de Extranjero), which starts and ends with a letter and contains seven numerical digits.