A man has been arrested on suspicion of murder after a grandmother was bludgeoned to death as she house-sat for friends more than five years ago.
Artist Valerie Graves, 55, was found dead in bed at around 10am on December 30 2013, on the ground floor of a £1.6 million house by the sea in Bosham, West Sussex.
Cristian Sabou, 28, was arrested on a European arrest warrant on Wednesday morning at his home in Dej, in the north-western part of his native Romania, Sussex Police said.
The warrant was granted by a UK judge and his extradition is now being sought through the Romanian courts.
He will appear in Cluj-Napoca to face extradition proceedings on a time and date yet to be confirmed.
If the extradition is successful, he will be brought to court in Sussex, police said.
Detective Chief Inspector Jon Fanner said: "This is a major development in our task of achieving justice for Valerie and her family.
"It follows detailed inquiries in Romania by officers from the Surrey and Sussex Major Crime Team, in which we were assisted by valuable liaison with local law enforcement officers of the General Police Inspectorate, Criminal Investigations Directorate, Bucharest, the Criminal Investigation Service in Cluj, and the Special Operations Brigade in Cluj, also the local prosecutor.
"We have worked closely with the Crown Prosecution Service throughout and they have authorised the prosecution. We have also had valuable support from the National Crime Agency's overseas network.
"We now hope to ensure, subject to the decision of the Romanian courts and judicial authorities, Sabou's return to this country for an appearance before magistrates with a view to his being sent for crown court trial."
On the fifth anniversary of Ms Graves's death last December, relatives told how no-one had given up hope on the investigation but there was a sense police had exhausted all lines of inquiry.
At the time, Sussex Police confirmed it had ended a huge DNA screening programme which saw almost 3,000 men tested. But detectives pledged to continue investigating.
Ms Graves had moved from Scotland to Bracklesham Bay, West Sussex, shortly before her death.
She died just days after her birthday while house-sitting at the Smuggler's Lane mansion – with her mother Eileen, her sister Jan and her sister's partner Nigel Acres – for family friends the Chamberlains who were on holiday in Costa Rica for Christmas.
Last seen alive at around 10pm the night before, there were no signs of a struggle.
But a post-mortem examination found she had severe head injuries after being hit with a claw hammer, probably at around midnight.
Sussex Police then launched one of the biggest investigations in its history.