A woman suffered serious head injuries after being “attacked with a hammer” in a quiet country lane.
The victim, whose age is not known, was taken to hospital after being found in Telegraph Lane in Claygate, Surrey at about 1.15pm on Monday.
Detectives believe she was targeted in an unprovoked attack.
A 22-year-old man was arrested soon afterwards and was being questioned today on suspicion of attempted murder.
Surrey Police Investigating officer, Temporary Detective Inspector Sean West said: “This appears to have been a completely unprovoked attack.
“Such violent and senseless attacks are thankfully extremely rare in our local communities and I would like to reassure you that we are working around the clock and doing everything possible to ensure the person responsible is brought to justice.”