CREATE TABLE table_19259 ("AGR Power Station" TEXT, "Net MWe" FLOAT, "Construction started" FLOAT, "Connected to grid" FLOAT, "Commercial operation" FLOAT, "Accounting closure date" FLOAT)

What year did construction start at Heysham 1
SELECT "Construction started" FROM table_19259 WHERE "AGR Power Station" = 'Heysham 1'
SELECT "Construction started" FROM "table_19259" WHERE "AGR Power Station" = 'Heysham 1'