The suspect was identified only as a 22-year-old native of County Tyrone in Northern Ireland, The Guardian reported. He was arrested by an English anti-terrorism unit, a spokesman for the Police Service of Northern Ireland said.
Police Constable Ronan Kerr was killed at his home in Omagh in 2011 by a bomb attached to his car. Investigators believe the killing was the work of dissident Irish Republicans who have refused to support the peace agreement.
Before the arrest in Milton Keynes, Buckinghamshire, police in England and Northern Ireland carried out searches of locations in Omagh and Cumbria, the PSNI said.