When was there a development rate of £4.92?
CREATE TABLE "current_and_past_rates" (
  "from" text,
  "adult_rate" text,
  "development_rate" text,
  "16_17_year_olds_rate" text,
  "apprentice_rate" text
);
SELECT "from" FROM "current_and_past_rates" WHERE "development_rate"='£4.92';