Detectives from Crumlin Garda station, Dublin, were in London last night to question an English national as part of their investigation into the murder of a 29-year-old woman in Walkinstown.
It was understood the Englishman was interviewed last night by the Irish detectives.
London police were this morning expected to apply for an extension to the man's detention in order to give gardaí more time to interview him further today.
Ms Georgina Eager, from Co Wicklow, was found dead late on Thursday night by members of her family who then alerted gardaí. She had been stabbed and badly beaten, according to a Garda source.
Gardaí said Ms Eager had known the man being held in England, but the exact nature of their relationship was not yet clear.
"We are still trying to determine if they were in a relationship of if they knew each other in some other way," one source said.
Ms Eager, originally from Newtownmountkennedy, had been living at the house on St Peter's Road, Walkinstown, where her remains were discovered in an upstairs bedroom. She had lived there for over a year and was understood to be working in a health clinic close by.
Her family became concerned for her safety after attempts to contact her on Thursday failed. They reported their concerns to gardaí, and at least one member of the family went to the house on St Peter's Road where the dead woman's remains were discovered at around 11.30 p.m.
The family alerted gardai immediately, and detectives from Crumlin station began a full murder inquiry. The scene was sealed off late on Thursday, and forensic experts carried out a full examination of the house yesterday.
The man being held in London last night is understood to be in his late 50s or early 60s.
He was detained by officers from the London Metropolitan Police. It had been widely reported yesterday that the man was detained at Heathrow Airport as a result of a minor offence.
However, the police in London last night confirmed he had been detained about 40km from Heathrow in the south-west London suburb of Kennington late on Thursday.
He was being held in connection with "an incident in Dublin on Thursday", a police spokeswoman said.
While the man had been initially arrested on a public order matter in Kennington, British police contacted gardaí after they learned their prisoner had an address at Walkinstown. They then detained him in relation to the Dublin murder.
The Deputy State Pathologist, Dr Marie Cassidy, was carrying out a post mortem examination of the body in the City Morgue late yesterday.
It was understood that the dead woman had been stabbed in the neck and that she may also have been beaten during the attack with claimed her life.
The results of the post-mortem were not expected until some time today.
