The man believed to be the owner of the dog which mauled to death a woman at her home was arrested tonight.
Alex Blackburn-Smith had been urgently sought by police following the victim's death last night at a house on Demesne Road, Wallington, south London. She was named locally as Barbara Williams.
The Belgian mastiff, described by one officer as large and ferocious, was shot dead by police marksmen.
Tonight, a Metropolitan Police spokesman said: "A 34-year-old man has this evening attended a south London police station and has been arrested on suspicion of manslaughter and suspicion of cultivating cannabis."
Sources confirmed that the arrested man was Blackburn-Smith.
The Metropolitan Police spokesman said the victim was thought to be aged in her 50s.
He said: "A post-mortem will be scheduled in due course. We await next of kin, and formal identification.
"An inquest will open and adjourn in due course. Armed police destroyed the dog - believed to be a Belgian mastiff - and one puppy has been removed from the property.
"Detectives from Sutton borough are investigating."
Earlier, Detective Chief Superintendent Guy Ferguson said Blackburn-Smith was the main occupier of the premises.
Mr Ferguson said he believed the victim was a lodger at the property which was "controlled" by Blackburn-Smith.
He described the dog as "distinctly large" and said that at the time of the attack another woman of similar age to Ms Williams was in the house with a child under five.
"It was a very ferocious dog," he said.
"The officers had to use shields to contain the dog."
He said police would be investigating previous complaints about the dog and what, if anything, was done.
Sutton Council confirmed it had received a complaint about dogs damaging a neighbour's fence last year.
"The council and the police's Safer Neighbourhood Team were contacted in connection with another smaller dog and damage to a fence at this address in August 2009," said councillor Colin Hall, responsible for dog control.
"At that point there were no legal grounds for the council to intervene on the basis of our statutory powers.
"There were no subsequent complaints."
Next-door neighbour Burhan Yanbolu, a father of twin girls, said: "We didn't have anything to do with them because of the dog.
"It was a big strong dog.
"We started having problems with them in autumn 2009.
"There were two dogs and the big one would lean against the fence and could see over it on its hind legs.
"We had concerns it would get over and could get in our garden.
"Last year our children couldn't play in the garden at all because the mastiff damaged a big chunk of fence crashing through."
Describing last night's horrific events, Mr Yanbolu said: "The police came through our garden to get access.
"We could hear them talking about the female, saying she was badly injured and there was lots of blood, but they couldn't get in to secure the dog.
"Somehow the dog went into a different bit and the police and paramedics worked on the lady."
He said police marksmen evacuated neighbours on the other side and considered moving him and his wife as well.
"They told us to expect 10 rounds to take the dog out," said Mr Yanbolu.
"But it was only four. We heard three and then 30 seconds later there was one more."