Stephen Lawrence's brother and sister are still affected by his racist murder, reveals his mother Doreen Doreen Lawrence said Stuart and Georgina try not to dwell on tragedy But she admitted 1993 death in south-east London will never leave them His parents were forced to fight against institutional racism in the police Also faced battle against incompetence in initial probe into his murder Last year Gary Dobson and David Norris were jailed for role in killing Today 20th anniversary marked with service at central London church The siblings of murdered teenager Stephen Lawrence have had their lives affected "more than anyone could know" in the 20 years since his death, their mother revealed today. Doreen Lawrence, 60, said Stuart and Georgina try not to dwell on the tragedy but it will never leave them, two decades after their 18-year-old brother was murdered by racists as he waited for a bus. His parents, Doreen and Neville, were forced to fight against institutional racism in the police and incompetence in the initial investigation into his murder in Eltham, south east London, in April 1993. Remembered: Doreen Lawrence (left), mother of Stephen Lawrence, with Prime Minister David Cameron (right) before a memorial service at St Martin-in-the-Fields Church in Trafalgar Square, central London Family: Doreen Lawrence (right) with her son Stuart (left), brother of Stephen, before the service in London Gary Dobson, 37, and David Norris, 36, were jailed for life for their role in the murder. But three of the other prime suspects named on the famous Mail front page in 1997 continue to evade justice. Mrs Lawrence said of Stuart and Georgina: "Their lives have been affected more than anyone would know from the outside. They do the best they can and, like me, they don't really dwell that much. But you know in their moments how depressing it is for them. They've got their own families now. So, like we all do, they try to move forward and make the best of what they have. But those moments are always there - you can't get rid of them. Earlier this year, a racist, threatening letter directed at Stuart was sent to the charitable trust set up in his brother's memory - the first time that he had been targeted. Mrs Lawrence has received threats herself before and is used to a memorial plaque to her son being vandalised. The Stephen Lawrence Centre in Deptford, south-east London, has also been damaged. Attending: Premier League footballer Jermain Defoe (left) and singer Emeli Sandé (right) were at the service Support: Former Premier League footballer Sol Campbell arrives at the service at St Martin-in-the-Fields She said: "Any time anything happens that brings Stephen's name to the forefront we get something. Shocking case: Stephen Lawrence was murdered by racists in Eltham, south east London, in April 1993 "Whoever it is, they don't like to hear Stephen's name, they think "He's dead, let's move on, let's forget about it." It's fine for them, they can, but for us we don't want to forget about him. He was part of our lives and we don't want to forget about him. There are still individuals out there for whom Stephen's name seems to resonate not for good but for bad. But Stephen never did anything wrong to anybody. She said aspiring architect Stephen was "no different" from any other teenager, but he could have had a bright future. "Stephen was just an ordinary young man," Mrs Lawrence said. He enjoyed music, he loved fashion. He was an academic so he had a future. Stephen was special to us because he was our child, but he wouldn't be special to anybody else, he was just an ordinary young man growing up. He knew what he wanted and he would have achieved what he wanted, given the opportunity. He was no different to any young man growing up. The shambolic police handling of the initial probe into Stephen's death led to the Metropolitan Police being branded institutionally racist and coming under fire for an incompetent inquiry. Mrs Lawrence said she can "only hope" the force has changed in two decades. She said: "I can't say they definitely have changed. I don't think anybody knows apart from those who are working inside. Together: (l-r) Policing Minister Damian Green, Home Secretary Teresa May, DPM Nick Clegg, Doreen Lawrence, Stuart Lawrence, PM David Cameron, Labour leader Ed Miliband and London Mayor Boris Johnson Memories: An order of service for the memorial is shown outside St Martin-in-the-Fields Church in London There are those who are trying their best to make a difference, but does it actually feed down to the officer on the beat who actually carries out the work? You don't know. To say that the Met has changed, you can only hope. He was no different to any young man growing up Doreen Lawrence When Dobson and Norris were finally convicted last year, Scotland Yard stressed that it had changed as a force and had learned lessons from the case. The prosecution team in the trial, Mark Ellison QC and Alison Morgan, are now leading a review looking at whether there is evidence of corruption in the original investigation. Claims were made by lawyers acting for the Lawrence family that some officers may have been influenced by Norris's drugs baron father, Clifford Norris. But Mrs Lawrence fears there may not be enough information in police records to come to a definite conclusion. "I think they're doing mainly paper-based stuff," she said. You begin to wonder what information do they have to look into? You suspect and you believe that there must be some corruption. Political leaders: Doreen Lawrence with Deputy PM Nick Clegg (left) and London Mayor Boris Johnson (right) Stronger together: Doreen Lawrence with singer Beverley Knight (right) before the memorial service in London But how do you actually get to the root of it and get the truth out if they weren't making notes that could be followed up on? The mother of three said she does not see the case of her son's murder as unique. "The only way you can say it's unique is because we have kept the pressure up on the police," she stated. In respect: London Mayor Boris Johnson lights a candle during a memorial service for Stephen Lawrence I don't see the case as being unique in itself because there have been other murders and continue to be other murders where families are still waiting for justice. It's only because we have pursued and kept up the pressure why it comes across as being unique. Today she marked the 20th anniversary milestone with a memorial service at St Martin-in-the-Fields near Trafalgar Square in central London. Mrs Lawrence told the congregation: "I've always tried to look forward and to focus on the positive since Stephen's murder, and looked to see how I can make the lives of others better. The pain of losing someone never goes away, you just learn to live with it at cost. Over the years as a family we have mourned in our separate ways, not daring to speak out loud about our feelings. My pain is raw, and that of my children. She said it is difficult to believe that 20 years have passed since her son's death. It's hard to believe it has been that long. When you're young 20 years seems so far away, you can't imagine it," she said. It's difficult and I think Stephen's death will be something that is always at the forefront of my mind, and it will feel unbelievable that something like this could happen. In your quiet moments it's always there. It's not something you can just close the shutter and it will go away. The Stephen Lawrence Trust was set up to help young people from disadvantaged backgrounds to have a better future. Talking: Doreen Lawrence speaks to David Cameron (right) as they leave the service with Stuart (centre) Photocalls: Doreen Lawrence with Metropolitan Police Commissioner Sir Bernard Hogan-Howe (left) and Home Secretary Theresa May (right) Going in: Doreen Lawrence and her son Stuart (second left) attend a service at St Martin-in-the-Fields Emotional: Doreen Lawrence makes a speech during a memorial service for her son Stephen Lawrence Mrs Lawrence said: "I believe that Stephen's life had value. His life is giving life to other young children. For me there are times when you're angry about certain things, but then you always have to look at the positive. You always have to look forward, because if you don't look forward then life just stands still. Today the charity called for continued action to improve racial equality in Britain. A change obviously has taken place since that dreadful murder 20 years ago, a change in policing. But perhaps as important is the change in culture, of just not accepting racism in our country Prime Minister David Cameron Chairman Symon Sentain said: "While there has been progress in the 20 years since Stephen's death, not enough has changed. Social justice remains the focus of the Trust and we will continue to campaign, ensuring the lessons from Stephen's murder are acted upon. Britain cannot afford to waste talent. We need to have an inclusive and diverse workforce and encourage young people to transform their lives, overcome disadvantage and begin ambitious careers as professionals. However, in order to do this, government and statutory bodies need to lead the way and ensure that all public policies are fair, inclusive and meet the needs of diverse communities. The Trust has backed 100 young people to study to become architects, and is now supporting five young black law students on the road to becoming partners at Freshfields Bruckhaus Deringer. Thoughts: Prime Minister David Cameron gives a reading during a memorial service for Stephen Lawrence Solemn: Prime Minister David Cameron is pictured reacting to the service in Trafalgar Square, central London Thoughtful: Prime Minister David Cameron (centre), Labour leader Ed Milliband (right) and Deputy Prime Minister Nick Clegg (second left) inside the church during a memorial service for Stephen Lawrence Speaking: Bishop of London Dr Richard Chartres during a service for Stephen Lawrence at the London church Speaking to BBC News, Prime Minister David Cameron said: "A change obviously has taken place since that dreadful murder 20 years ago, a change in policing. But perhaps as important is the change in culture, of just not accepting racism in our country. We have made huge steps forward on that front, but there is always more that needs to be done. Today is also a day to pay tribute to Doreen and Neville Lawrence, who have shown incredible strength as they fought, and continue to fight, for justice for their son And in a statement ahead of the service, Labour leader Ed Miliband said: "My thoughts are with Stephen Lawrence's family and friends as we mark the 20th anniversary of his brutal murder. Stephen Lawrence's death exposed the deep-seated racism in parts of our society, including within the police. Over the last 20 years, this has dramatically improved, but we must continue to ensure that people in our society are not discriminated against because of the colour of their skin. Today is also a day to pay tribute to Doreen and Neville Lawrence, who have shown incredible strength as they fought, and continue to fight, for justice for their son. What is truly remarkable about them is that, out of tragedy, they have also sought to make a difference through founding the Stephen Lawrence Trust for young people from disadvantaged backgrounds. Their work and courage deserve our admiration and support. The first candle at the service at St Martin-in-the-Fields in Trafalgar Square, central London, was lit by Doreen Lawrence and her surviving son Stuart, dedicated to building hope in memory of Stephen. Prime Minister David Cameron read Our Last Awakening by John Donne, while Leader leader Ed Miliband and Home Secretary Theresa May gave readings from the Bible. There was also an address by Bishop of London Dr Richard Chartres, who said he would have liked to have known Stephen. The music spanned traditional hymns, through to Gospel and a rendition of Fallen Soldier by singer Beverley Knight who has performed the same song, especially written for Stephen Lawrence, at previous memorials. Mayor of London Boris Johnson told the congregation: "On a dark street in Eltham 20 years ago there took place a crime that caused shock and pain, and disbelief, and outrage. And it was left to those who had suffered the greatest pain and loss, the family of Stephen Lawrence, to search for the truth and for justice. But he said that the success of the Olympics had shown the best of the diversity of London, stating: "The world was watching us, and they saw that incorrigible happiness and that unity in diversity. And what people prophesied five decades ago would be a defect and difficulty in our society has been alchemised into the genius and magic of London. Address: Doreen Lawrence and her son Stuart (centre) during a memorial service for Stephen Lawrence Of course it has not happened easily. It is thanks to the work of countless thousands. It is thanks to Doreen and of course to Stephen, too, because it was the campaign for justice in his name that became the blueprint for change. On a dark street in Eltham 20 years ago there took place a crime that caused shock and pain, and disbelief, and outrage Mayor of London Boris Johnson And that benign change has happened, and is happening and will keep happening And out of that dark night 20 years ago has come great hope, and it is in a spirit of hope for London, the greatest city on earth, that we remember Stephen Lawrence today. The service today included the hymn Be Still for the Presence of the Lord, which has been sung at every memorial service for Stephen since he died. Guests included pop star Emeli Sande, Duwayne Brooks - Stephen's friend who was with him on the night that he died, and lawyers Michael Mansfield and Imran Khan who have represented the Lawrence family throughout their battle for justice. Metropolitan Police Commissioner Sir Bernard Hogan-Howe also attended the service, the theme of which was "building for the future." His predecessors have been invited to the event, despite the troubled history of the investigation into Stephen's murder.