the uk albums chart is a weekly record chart based on album sales from sunday to saturday in the united kingdom. albums are defined by the official charts company (occ) as being a type of music release that features more than four tracks and lasts longer than 25 minutes. during the 1970s, sales of albums in the united kingdom were compiled on behalf of the british music industry by the british market research bureau (bmrb). panel sales from approximately 250 (later expanded to 450) representative record stores across the uk were collected each week, and a multiplier figure would then be applied to these panel sales figures to obtain an estimate of the total sales across the country and to compile the weekly chart. each week's number one was first revealed at 12.45 pm on thursdays on the lunchtime show on bbc radio 1, and then moved to 6:05 pm (later 6:30 pm) on wednesday evenings during the peter powell and bruno brookes shows.