By Paul Byrne The Grand National festival starts today with police throwing a tight security ring around the Aintree racecourse. More than 150,000 punters will descend on Liverpool for three days of top class sporting action. They will be greeted by a huge police presence at the track, with armed officers joining colleagues on horseback and in plain clothes to ensure the event passes off peacefully. The highlight of the festival will be the 176th running of the Grand National on Saturday. Last year’s big race was disrupted by animal rights activists who ran onto the track, delaying the start f…