Thatcher compiled research into population data and centenarians and contributed a significant body of scholarly work in addition to his government statistics duties.

His work on the Kannisto-Thatcher Database on Old Age Mortality is held by the Max Planck Institute for Demographic Research and regarded as one of its most vital collections.

[4] He was mobilised as part of national service, instructed briefly in meteorology, and went to assist pilots in the Royal Navy with weather analysis.

[2] Under the newly formed version of the same agency in 1968, subsequently titled the Department of Employment and Productivity, Thatcher served as director.

[2] His work on the 1981 census in the United Kingdom in this role proved to be a difficult task, primarily due to the sheer size of total effort required for the operation.

[5] At a 1981 meeting in Sussex held by the Medical Journalists Association, Thatcher presented the findings from his research and called the results "spectacular".

[6] Thatcher posited that the increase in longevity amongst those individuals that actually get to one-hundred was likely attributable to lack of stress in these older years.

[6] Thatcher found that contributing factors towards this progress in longevity also included better overall healthcare and an ever-increasing total population size in general.

[8][9] He asserted that a fair number of individuals born between the 1950s–1960s attributed to the post–World War II baby boom would see a life expectancy age range between 116 and 123 total years.

[4] His work on the Kannisto-Thatcher Database on Old Age Mortality is held by the Max Planck Institute for Demographic Research and regarded as one of its most vital collections.

[10] Academic scholars James Vaupel and Väinö Kannisto helped him co-author the book The Force of Mortality at Ages 80 to 120, which was first published in 1998.