Detectives investigating the dissident republican murder of policeman Ronan Kerr in Northern Ireland are questioning a 22-year-old man.
The man, from Omagh, Co Tyrone, was arrested in Milton Keynes, Buckinghamshire, the Police Service of Northern Ireland said.
The newly-recruited Catholic constable, 25, died when a bomb exploded under his car at his Omagh home last year.
A PSNI spokesman said: "A 22-year-old man from Omagh has been arrested in England as part of the ongoing investigation into the murder of Constable Ronan Kerr and linked incidents.
"The arrest took place in Milton Keynes earlier this evening and was made by officers from the North West Counter Terrorism Unit at the request of PSNI Serious Crime Branch detectives."
The suspect was taken to a police station in England for questioning.
Searches carried out in Omagh and Cumbria have been completed. A number of items were seized for examination, including a lorry stopped in Milton Keynes. Police inquiries are continuing.
Mr Kerr's death was blamed on dissident republicans opposed to the peace process.
He was from a nationalist background, brought up in a village near Omagh, and his killing caused revulsion among members of the local community.
Dissident republicans have killed policemen, soldiers and prison officers as part of their campaign and the threat level remains severe.