A man was being questioned last night over the attempted murder of Abigail Witchalls, the mother left paralysed after she was stabbed in the neck.
The suspect, aged 25, was among several dozen people named during more than 400 telephone calls from the public after an appeal for information about the attack in Surrey.
He is expected to be included in a video ID parade that will be shown to the young mother as she lies in her hospital bed.
The suspect is understood to have attended Croydon police station on unrelated matters earlier on Wednesday night. He was then arrested by officers from Surrey police.
He was taken by police to Staines police station yesterday lunchtime. Forensic specialists were searching the suspect's home yesterday, a terraced house on an estate in New Addington, Surrey. A police source described the arrest, made at 11pm on Wednesday night, as "significant, but not necessary conclusive".
Detectives are still trying to find the blue estate car that was used by the attacker, who struck in a country lane in Little Bookham on Wednesday last week.
Mrs Witchalls has told police her attacker held a knife to the throat of her 21-month-old son, Joseph before stabbing her.
Mrs Witchalls was described as being in "good spirits" yesterday and was continuing to make slow progress. She is paralysed from the neck down and has been getting physiotherapy. She cannot speak, but has been able to describe her assailant by mouthing simple words and blinking during nine hours of questioning in her hospital bed by two women detectives. Police officers have been posted outside St George's Hospital in Tooting, south London, to reassure Mrs Witchalls and her family.
A police spokeswoman added: "Obviously there is a possibility, as in any other similar case, the offender might try to find her."
Police have emphasised that the latest arrest is only one line of inquiry.
Among the continuing work is an extensive forensic search for DNA samples that the attacker may have left on his victims or at the crime scene.
The National Crime Faculty had drawn up a profile of the background of the likely attacker for Surrey Police. The police said they were particularly interested in speaking to people with a history of violence. A man, 28, who owns a blue car seen near Little Bookham at the time of the attack, and a woman, 29, who were arrested last week, have been eliminated from police inquiries.
Mrs Witchalls relayed to police how she had been coming from a mother and toddler group when she first saw her attacker in a blue car on the lane.
She became nervous as their eyes met and tried to run away along a narrow track after seeing that the car had been parked and that the man was coming towards her.
The attacker was described by Mrs Witchalls as aged 20 to 35 and was wearing looped silver earrings, and spoke with a cockney or southern accent. He may have been under the influence of drink or drugs.Reuse content