CREATE TABLE table_20580 ("Platform" FLOAT, "Frequency  ( per hour ) " FLOAT, "Destination" TEXT, "Service Pattern" TEXT, "Operator" TEXT, "Line" TEXT)

Who is the operator to Highbury & Islington?
SELECT "Operator" FROM table_20580 WHERE "Destination" = 'Highbury & Islington'
SELECT "Operator" FROM "table_20580" WHERE "Destination" = 'Highbury & Islington'