In which year was the Grand National horse race run on the Monday instead of the usual Saturday?

The Grand National is a National Hunt horse race held annually at Aintree Racecourse, near Liverpool, England. The first run in 1839, it is a handicap steeplechase over an official distance of about 4 miles and 2½ furlongs, (or accurately 4 miles 514 yards (6.907 km)), with horses jumping 30 fences over two laps. It is the most valuable jump race in Europe, with a prize fund of £1 million in 2017. An event that is prominent in British culture, the race is popular amongst many people who do not normally watch or bet on horse racing at other times of the year.

The 1997 Grand National was postponed after two coded bomb threats were received from the Provisional Irish Republican Army. The course was secured by police who then evacuated jockeys, race personnel, and local residents along with 60,000 spectators. Cars and coaches were locked in the course grounds, leaving some 20,000 people without their vehicles over the weekend. With limited accommodation available in the city, local residents opened their doors and took in many of those stranded. This prompted tabloid headlines such as "We'll fight them on the Becher's", in reference to Winston Churchill's war-time speech. The race was run 48 hours later on the Monday, with the meeting organisers offering 20,000 tickets with free admission.