The mother of murdered teenager Stephen Lawrence has said her "pain is raw", at a memorial service to mark the 20th anniversary of her son's death.
The 18-year-old aspiring architect was murdered in a racist attack as he waited for a bus in Eltham, south east London, on 22 April 1993.
The memorial service took place at St Martin-in-the-Fields, near Trafalgar Square in central London.
Doreen Lawrence said: "My pain is raw, and that of my children."
She added: "Over the years as a family we have mourned in our separate ways, not daring to speak out loud about our feelings.
"As a result of Stephen's murder, I was brought into an activist's role, one that I was not prepared for. It was like walking in the dark during the early days and, at times, it still feels that way."
Earlier, London's police chief Bernard Hogan-Howe - who also attended the service - vowed to prosecute all of those involved in the killing.
After taking too long, we did
get convictions in two cases
last year, and what we're
going to do is catch the other
Mrs Lawrence was joined at the event by relatives, friends and senior political figures including Prime Minister David Cameron, Deputy Prime Minister Nick Clegg, Labour Party Leader Ed Miliband and London Mayor Boris Johnson.
Other guests included pop star Emeli Sande, Duwayne Brooks - Stephen's friend who was with him on the night that he died - and lawyers Imran Khan and Michael Mansfield who have represented the Lawrence family throughout their battle for justice.
A number of supporters of The Stephen Lawrence Charitable Trust, which Ms Lawrence set up to help young people from disadvantaged backgrounds, also attended.
Mr Cameron read Our Last Awakening by John Donne, while Mr Miliband and Home Secretary Theresa May gave readings from the Bible.
There was also an address by Dr Richard Chartres, the Bishop of London, who said he would have liked to have known Stephen.
'Pain and loss'
The music ranged from traditional hymns, to Gospel and a powerful rendition of Fallen Soldier by singer Beverley Knight who has performed the same song, especially written for Stephen Lawrence, at previous memorials.
The service included the hymn Be Still for the Presence of the Lord, which has been sung at every memorial service for Stephen since he died.
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."
Stephen's father Neville has chosen to remember his son privately in Jamaica, taking flowers to his grave and saying a prayer with a friend who is a pastor.
Two men, Gary Dobson, 37, and David Norris, 36, were jailed for life last year after being found guilty of the attack.
Sir Bernard Hogan-Howe, who attended the service, said it had taken "too long" to convict the pair.
He said: "After taking too long, we did get convictions in two cases last year, and what we're going to do is catch the other people involved."
The investigation was initially mired in allegations of police incompetence and institutional racism.
Sir Bernard said the police had "improved greatly" in the years since the murder, and that there were now around 3,000 black and ethnic minority officers in the Met.