Mental health problems are often said to affect one in four people in Britain, although with no consistent explanation of what the figure includes. We used three English national population surveys of psychiatric morbidity from 2000, 2007 and 2014 to provide prevalence rates for recent psychiatric problems. We combined disorders progressively to demonstrate the effects of cumulation. Psychosis had a prevalence of around 1%, severe common mental disorders added about 8%, and including less-severe common mental disorders gave a value around one in six. The figure of one in four required the inclusion of various other disorders. These values were strikingly stable over the surveys.