A woman reported to be an American spy working at GCHQ, the UK's intelligence, security and cyber agency, has been stabbed outside a leisure centre in Cheltenham.
She was taken to hospital after last week's attack in south-west England, and remains in a stable condition.
A man, 29, has been arrested on suspicion of terrorism offences and attempted murder, said police.
He was initially detained on suspicion of attempted murder, following the incident that took place at around 9.15am on March 9.
The suspect was then re-arrested under the Terrorism Act, on suspicion of the commission, preparation or instigation of terrorism and on suspicion of preparing acts of terrorism.
He is currently being questioned by officers from Counter Terrorism Policing.
Assistant chief constable Richard Ocone of Gloucestershire Constabulary said police believe that it was an “isolated” incident.
He said: “I would like to reassure those living locally or visiting the county that we believe this was an isolated incident and we are not aware of any wider threat to members of the public.
“We are working closely with our partners in Counter Terrorism Policing.”
The incident is being investigated by Counter Terrorism Policing South East, working alongside Counter Terrorism Policing South West and officers from Gloucestershire Constabulary.
Details of the victim and incident are being kept confidential.
However, it is known that the woman was sitting in a car in the leisure centre car park at the time of the attack, and managed to get out of the vehicle to find help.
According to some reports, she is a US intelligence officer on secondment to GCHQ.
GCHQ headquarters is 5km from the scene of the attack. The US intelligence community has a strong relationship with the UK intelligence agency.