Police questioned two men on Wednesday in connection with the 1993 killing of a black teenager, while a separate race-crime squad picked up dozens of people in raids around the capital.
The brutal murder of 18-year-old Stephen Lawrence by a gang of white youths and the failure of the police to adequately investigate his death prompted a national debate on racism and on police handling of such crimes.
Five white youths were identified as suspects after the April 1993 killing in east London, but none has been successfully prosecuted.
The two new arrests were made on Tuesday night as Lawrence's family appealed on a BBC programme for anyone with information about the slaying to contact police.
A separate series of police raids targeting known racists resulted in the arrest of dozens of people on Wednesday on suspicion of several offences, including threats to kill and racially aggravated criminal damage. The task force on racial and violent crime started its raids across London at 6:30am and continued throughout the day.
By mid-afternoon, officers had arrested 62 people, but Detective Chief Superintendent John Godsave said the number was expected to rise to at least 80. The arrests did not appear to be linked to any far-right racist group or the Lawrence case, he said.
But repercussions of that case continue. Following a public inquiry and a scathing report that found the London police institutionally racist, the government pledged to take a more active role in combating racial intolerance.
Wednesday's raids stemmed from the work of "community safety" units set up in June in all the capital's 32 boroughs to target those responsible for racist crimes.
Godsave said some 300 officers have been gathering information since February, many working closely with victims of racist and homophobic crimes.
"There is nothing to suggest these people are overtly political or the individuals involved are known to each other," Godsave said. "But if these arrests make the community feel like they can come forward and trust us, then I suppose you can say they are linked."