s , ▁sales ▁of ▁albums ▁in ▁the ▁United ▁Kingdom ▁were ▁compiled ▁on ▁beh alf ▁of ▁the ▁British ▁music ▁industry ▁by ▁the ▁British ▁Market ▁Research ▁Bureau ▁( B MR B ). ▁P anel ▁sales ▁from ▁approximately ▁ 2 5 0 ▁( l ater ▁expanded ▁to ▁ 4 5 0 ) ▁representative ▁record ▁stores ▁across ▁the ▁UK ▁were ▁collected ▁each ▁week , ▁and ▁a ▁multip lier ▁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 ▁week ly ▁chart . ▁Each ▁week ' s ▁number ▁one ▁was ▁first ▁revealed ▁at ▁ 1 2 . 4 5   pm ▁on ▁Th urs days ▁on ▁the ▁l unch time ▁show ▁on ▁BBC ▁Radio ▁ 1 , ▁and ▁then ▁moved ▁to ▁ 6 : 0 5   pm ▁( l ater ▁ 6 : 3 0   pm ) ▁on ▁Wed nes day ▁even ings ▁during ▁the ▁Peter ▁Pow ell ▁and ▁Bruno ▁Brook es ▁shows . ▁ ▁The ▁official ▁charts ▁of ▁the ▁best - s elling ▁singles ▁and ▁albums ▁of ▁the ▁ 1 9 7 0 s ▁were ▁compiled ▁by ▁B MR B ▁and ▁published ▁in ▁Music ▁Week ▁in ▁the ▁issue ▁dated ▁ 2 2 ▁December ▁ 1 9 7 9 , ▁and ▁the ▁top ▁ 1 0 0 ▁singles ▁and ▁albums ▁were ▁counted ▁down ▁throughout ▁the ▁day ▁on ▁Radio ▁ 1 ▁on ▁ 3 1 ▁December ▁ 1 9 7 9 , ▁playing ▁one ▁track ▁from ▁each ▁of ▁the ▁top ▁ 1