Jail terms handed out to Gary Dobson and David Norris are only "partial justice" for Stephen Lawrence's family, the police watchdog said today.
The Independent Police Complaints Commission (IPCC) said "much remains to be done" as London mayor Boris Johnson added that the case is "certainly not closed".
Mr Johnson welcomed today's sentencing but added: "The failures in the Stephen Lawrence murder case have been a long-running sore for us as a city and an embarrassment to our police force.
"I, like everyone across the country, have always been in awe of the Lawrence family's dignified pursuit of justice. They are a fine example to us all.
"Today's sentencing is a reflection of their tireless determination and also sends a bold message to anyone else involved in this crime. This case is certainly not closed but I am relieved that some justice at last has been done."
Deborah Glass, of the IPCC, said the initial investigation into the murder was "truly shocking".
But she said Scotland Yard now deserved credit for the two prosecutions.
Ms Glass, deputy chairwoman of the watchdog, said: "Today's sentences can only be a partial justice for the family of Stephen Lawrence.
"But following yesterday's verdicts I would like to pay tribute to the extraordinary determination of the Lawrence family and all those who stood with them through their struggle to achieve justice for their son Stephen.
"There can be no doubt that in their struggle they were also instrumental in bringing much-needed fundamental reform to policing in this country. The Independent Police Complaints Commission, the result of a recommendation of the Stephen Lawrence Inquiry, is itself one of those reforms.
"It is important to acknowledge the changes that have been made over the past decade, but there is equally no doubt that much remains to be done to increase the confidence of black and minority ethnic communities in policing.
"To play our part, the IPCC will strive to ensure not only that our values embody the lessons learned from the Stephen Lawrence Inquiry, but also that our actions reflect the aspirations for justice on which those values are based.
"While the initial investigation into Stephen's murder was truly shocking in its negligence, I also want to acknowledge and give credit to the current Metropolitan Police investigation team.
"While nothing can diminish the family's pain for Stephen's loss or compensate for the initial failures of the investigation, the Metropolitan Police have since 2006 worked tirelessly to secure these convictions and to ensure that two racist killers will not be free for many years."
US civil rights campaigner Reverend Jesse Jackson said the length of the prison sentences "cheapens black life".
On a visit to the Occupy movement outside St Paul's Cathedral, he added that "justice delayed is justice denied".
When asked if the prison terms were long enough, he replied: "I don't think so, in the sense that they were teenagers when they did it but they were convicted 19 years later, so it does not give a comfort zone.
"Justice should be swift and sure. The killing was sure but the justice is incomplete because there are still killers on the loose.
"Somebody in the community who knows where the other three are has some moral obligation to let their conscience be their guidance and speak out."