State Drive Rehearsal - The State Coach with members of the Household Cavalry seen leaving Parliament square to continue along Whitehall during this morning's rehearsal of the state drive for the opening of Parliament. A rehearsal of the state drive to Westminster for the opening of Parliament on October 21st, was held this morning (Sunday), with the King's escort of Household Cavalry taking part. High police officials and officials of the Royal Mews timed the procession and checked details. October 12, 1947.