began in April 2007 and by the end of that year 50,000 people had taken part. Recruitment reached 100,000 in April 2008, 200,000 in October 2008, 300,000 in May 2009, 400,000 in November 2009 and passed the 500,000 target in July 2010. Participant enrollment was declared complete in August 2010. The volunteers were largely healthy, wealthy and white European. Rather than recruiting more participants into the biobank, the organisation is helping other institutions establish and run similar initiatives. Usage The UK Biobank dataset was opened to applications from researchers in March 2012. The resource is available to scientists from the UK and outside, whether they work in the public or private sector, for industry, academia or a charity, subject to verification that the research is health-related and in the public interest. Researchers are required to publish their results in an open source publication site or in an academic journal and return their findings to the UK Biobank. By April 2017 4,600 researchers had registered to use the resource, over 880 applications had been submitted and 430 research projects were completed or underway. 130 peer-reviewed articles based on the UK Biobank data had been published by January 2017. Extensions Since the completion of recruitment several new types of data have been added: During 2011-12 participants who supplied an email address were asked to assist by completing web-based dietary questionnaires, with the aim of combining a series of daily 'snapshots' to form a picture of overall nutrition. 176,012 of the participants responded at least once and 27,535 completed four questionnaires over a 16-month period. During 2012–13 25,000 participants at the Stockport centre were asked to attend the assessment centre to repeat the initial measurements. It was intended to repeat these assessments every few years. In 2013 to 2015, Axivity AX3 tri-axial wrist physical activity monitors were distributed to 100,000 participants, which recorded week-long triaxial acceleration at 100 Hz. This data was centrally processed, and listed on the Data Showcase. In 2014 and 2015 120,000 participants completed a questionnaire on cognitive functions. Four of the tests were repeats of the initial assessment and two tests (symbol digit substitution and trail making) were new. In 2015 and 2016, 117,500 participants completed questionnaires on occupational history and related medical information. In 2016 and 2017 137,400 participants completed questionnaires on mental health events including subjective well-being estimates, psychotic experiences, self-harm behaviours, traumatic events and cannabis and