Former Radio 1 DJ Dave Lee Travis has been arrested as part of the police probe set up in the wake of the Jimmy Savile scandal, the BBC understands.
Police said a man in his 60s from Bedfordshire was being held on suspicion of sexual offences.
The Met said their investigation into alleged abuse by Savile and others - Operation Yewtree - had so far recorded 200 allegations of sexual assault.
They have now identified about 450 potential victims of sexual abuse.
The arrest of Mr Travis, 67, is the fourth so far in connection with the Savile investigation.
In a statement, the Met said the latest arrest "falls under the strand of the investigation we have termed 'Others'", meaning the allegations are unrelated to Savile.
But the force said that the "vast majority" of the 450 possible victims were alleging sexual abuse by former BBC TV presenter and DJ Savile, who died last year aged 84.
Mr Travis has not been officially named by police, who made the arrest at 07:45 GMT.
The DJ - known by the nicknames DLT and the Hairy Cornflake - is best known for his 25-year stint on Radio 1
His career at the station came to an end in 1993 when he resigned on-air from his role, telling listeners he was unhappy with changes that were taking place.
Mr Travis also presented editions of Top of the Pops in the 1970s and 1980s.
He now presents The DLT Show, a radio programme on the Magic Network.
Bauer Media, which owns Magic Network, said it had no comment on the arrest.
The BBC has postponed the transmission of an edition of Top of the Pops from 1977 hosted by Mr Travis that was due to be shown on BBC Four at 19:30.
Another edition of Top of the Pops, which was presented by Kid Jensen, will go out in its place.
'Worse than feared'
The number of potential victims in the investigation into Savile has risen since last month, when police said they had identified about 300 people who say they were abused by the late entertainer and others.
BBC home affairs correspondent Danny Shaw said: "The police said a couple of weeks ago that Savile was a predatory sex offender - one of the worst sex offenders that they had come across.
"The figures that we are being given today suggest that the scale of his offending is even worse than was first feared."
Savile, a Radio 1 DJ and presenter of the Jim'll Fix It show on BBC1, was a household name in the 1970s and 1980s.
But since his death last year, details have emerged suggesting he was a paedophile who abused young people on BBC premises, in various care homes and even in Broadmoor psychiatric hospital, over a period of five decades.
The NSPCC said on Thursday it had received 236 calls about Savile - an average of five per day - since the first abuse allegations emerged last month.
Former pop star Gary Glitter was the first person to be arrested in connection with the Met's Savile abuse inquiry.
Glitter, 68, whose real name is Paul Gadd, was arrested on suspicion of sex offences and bailed until mid-December.
On 1 November police arrested entertainer Freddie Starr on suspicion of sexual offences.
He has denied claims made against him and was bailed after a number of hours of questioning.
On Sunday, former BBC producer Wilfred De'Ath, who is in his 70s, was arrested on suspicion of sexual offences. He was later bailed until December.