After a decade of sometimes troubled incubation, UK Biobank finally hatched just before Easter, its birth heralded by newspaper headlines promising a new dawn in researchers' understanding of the risk factors for human diseases.
The ?62 million project, funded primarily by the Medical Research Council and the Wellcome Trust, is by no means the first repository of biological samples. Nor, according to Douglas Easton, director of the Cancer Research UK Genetic Epidemiology Unit at the University of Cambridge, is it likely to live up to the original "hype" that it would be the means by which the fruits of the Human Genome Project would be realised.
"A lot of the understanding of the relationship between genes and disease has come about through other studies that already existed, (so) in a way the purpose of UK Biobank has changed ... there is now much more emphasis on it being a longitudinal study with a lot of data on diet and other biomarkers," he said.
Longitudinal studies are hardly unusual either. But according to Sir Rory Collins, UK Biobank's principal investigator and chief executive, no existing project can rival the size and detail of its sampling.
Between 2007 and 2010, half a million members of the public aged between 40 and 69 volunteered to undergo three hours of testing at 22 makeshift laboratories set up in shopping centres around the UK.
Data collected about them included their height, weight, grip strength, bone density, lung function, cardiac fitness, blood pressure and cognitive function. Samples were taken of their blood, saliva and urine, and they were asked detailed questions about their environment, lifestyle and life experiences.
They also agreed to grant researchers anonymised continuing access to their medical records so that subsequent GP visits, hospitalisations and deaths could be tracked.
A small subset of participants will be regularly reassessed and the results extrapolated to give an indication of how much measurements are likely to have changed across the cohort as time goes by.
Numerous further augmentations of the database are also planned. Subject to the agreement of the funders - which also include the British Heart Foundation, the Department of Health and the Scottish and Welsh governments - this will include sophisticated imaging of the brains, hearts and bodies of 100,000 participants.
Sir Rory, who is also professor of medicine and epidemiology at the University of Oxford, said that the size of the project meant that significant numbers of participants would develop a wide range of conditions. The genetic and environmental causes could be studied by comparing data about the group that developed them with a control group that did not.
Tim Bishop, professor of genetic epidemiology at the University of Leeds, said it was difficult to predict what the important research questions would be in 20 years' time. He added that some researchers would have liked more data to be gathered about the specific conditions they studied.
But he agreed that the range of data collected so far represented a "highly pragmatic solution to the complex problem of how [to] create a study which benefits many different aspects of medical science, especially when the benefits will not be [seen] for years...and the technologies are changing rapidly".
Sir Rory said the biobank had done everything it could to ensure that samples were collected and processed in ways that would allow the widest possible range of analyses - known as "assays" - to be carried out on them in the future.
In addition, a nearby backup facility stores the samples at lower temperatures than UK Biobank's main site in Stockport in case assays are invented that require it.
The biobank aims to carry out on all samples some standard assays that are likely to be widely requested. However, efficiency dictates that it be left to researchers to request other assays as cohorts of disease sufferers emerge.
Withdrawals welcome
The contract researchers sign with UK Biobank will oblige them to publish their analyses of its data - although not necessarily in open-access journals. Meanwhile, after a short delay to allow them to study the data and prepare papers, the raw information generated will also be added to the bank. According to Sir Rory, this meant that the resource would become more valuable the more people used it.
Although applications to the bank will be scrutinised, he emphasised that the intention was not to discourage use. Evidence of the scientific review of a proposed project by the organisation funding it would typically be sufficient to obtain access, and criteria will only be stiffened when projects are potentially controversial, involve contacting participants or require use of depletable samples.
The publication of raw data will also allow other groups to repeat analyses and highlight errors, which Sir Rory called "the purest form of peer review".
Maximal use of UK Biobank will also be promoted by the decision of its funders to commit another ?25 million to cover its running costs over the next five years - taking their total investment to ?93 million - and to charge researchers only for the cost of obtaining the information they want.
The resource, which officially launched on 30 March, is open to any "bona fide" researcher who wants to carry out health-related research "in the public interest".
Access will be granted on an equal basis to researchers regardless of whether they hail from the UK or overseas, and academic applications will be treated no differently from those from the public, private or voluntary sectors.
Sir Rory said UK academics' involvement in the genesis of UK Biobank would give them a "head start" in knowing how to make best use of it. However, he noted that Francis Collins, director of the US National Institutes of Health, had already convened a high-level meeting to consider how the NIH could make the most of the resource.
"That is good for UK Biobank because if the NIH invests in assays...it will enrich the resource and in a sense [the NIH will] become a funder of it," Sir Rory said.
He added that Professor Collins would "love" to establish a biobank in the US: "But they don't have the NHS structure in which to embed it and he came to the conclusion that it would be so expensive that even the Americans couldn't afford it."
Both Professor Easton and Professor Bishop expect to exploit UK Biobank - although they observed that its use would be limited until significant cohorts of disease sufferers began to emerge. However, according to Danny Altmann, head of pathogens, immunology and population health at the Wellcome Trust, it was already "the envy of the research world".
"Its value is limited only by the imagination and ingenuity of the researchers who want to use it because all the answers are in there," he said.