The Hillsborough stadium tragedy which shocked the sporting world is being remembered 20 years on. The FA Cup semi-final between Liverpool and Nottingham Forest should have been one of the highlights of the 1988-89 season, but it turned into one of the darkest days in English football history. On April 15, 1989, 96 Liverpool fans were crushed to death on an overcrowded terrace at Sheffield Wednesday's stadium. The game was stopped after just six minutes as desperate fans began climbing over safety fences, trying to escape the crush. As the full extent of events was realised, the game was abandoned and the pitch became littered with the dead and injured. Police and medics tried to revive many victims, while others were taken away on makeshift stretchers made from broken advertising boards. An official report into the disaster blamed senior police officers for not properly controlling the crowd. Thousands of people are expected to attend a memorial service on the Kop at Anfield where a representative of each victim's family will be awarded the Freedom of Liverpool. The commemoration will include a two-minute silence at 3.06pm and conclude with the singing of Liverpool's anthem, You'll Never Walk Alone. The bells of Liverpool's two cathedrals and its civic buildings will ring out 96 times in memory of each of the fans and the city's public transport will also come to a stop for two minutes at 3.06pm, exactly 20 years since the disaster. Ninety-six candles will be lit to remember each individual life that was lost. Liverpool's Lord Mayor, Steve Rotheram, said: "Hillsborough affected so many lives, not just on Merseyside but across the whole of the UK. I attended the match 20 years ago and the passing years do not diminish the importance and the poignancy of this occasion." Players past and present have insisted those lost will never be forgotten. For one current player the occasion will be particularly poignant. One of those who died in the disaster was Jon-Paul Gilhooley, cousin of Liverpool midfielder and England international Steven Gerrard. "It was a difficult time to know that one of your cousins was at that game and had been crushed. Seeing his mum and his dad and his close family, the reaction on their faces helped to drive me on to become the player I am today," said Gerrard. Gordon Brown has spoken of the memory etched in his mind of "heroic" Liverpool FC fans helping to save lives in the Hillsborough disaster. He said: "People will never forget that day; it's etched on our memories. "I remember how the Liverpool fans helped each other, coming to the aid of people who were in difficulty and trying to rescue fellow fans - both young and old. "I don't think we can ever forget the 96 people who died."