Detectives were tonight granted more time to continue questioning Joanna Yeates's landlord on suspicion of her murder.
Chris Jefferies, 65, was arrested yesterday morning and a magistrate tonight granted Avon and Somerset Police an extension to hold him beyond 7pm.
The development came after officers spent the day talking to Peter Stanley, 56, a neighbour of the retired public school teacher in Clifton, Bristol, who said he and Mr Jefferies helped start Miss Yeates's boyfriend's car the day she vanished.
Tonight, a force spokesman said: "Police have today, Friday December 31, been granted more time to question a 65-year-old man, arrested on suspicion of murder on Thursday December 30, by magistrates."
Mr Stanley recalled how he and Mr Jefferies used jump leads to start Greg Reardon's car, sending him on his way to Sheffield.
"It was a non-event at the time, but absolutely poignant now - what if we didn't get the car to start?" said Mr Stanley.
Hours after successfully starting the car, Miss Yeates, a landscape architect, disappeared and her snow-covered body was discovered more than a week later on Christmas Day.
Mr Stanley, who lives in a flat in the mansion to the right of Mr Jefferies' in Canynge Road, Clifton, is being treated by police as a witness, they confirmed tonight.
He drove away from his home in his maroon BMW with a detective and returned later in a marked police car before officers left him.
Mr Stanley said he did not think Mr Jefferies spoke to Mr Reardon about going away for the weekend, and added: "I wouldn't say there was anything tense between them."
He said: "I had only just charged up my car because it didn't work when I had gone to see a friend.
"I got a phone call from Mr Jefferies. I was asleep at the time and it was early evening.
"He asked if his tenant could borrow my jump leads.
"I think Chris Jefferies wanted to borrow my car, but I said I didn't want to take all the power out of it.
"So he said 'Fine', and he then brought his car - I think it was the Chrysler.
"I met Greg and Chris Jefferies at the edge of the property and walked toward the car.
"I got Chris Jeffries to position his car so the bonnets were alongside each other.
"Greg's car was in the gutter of the road, and Chris Jefferies' car was in the road."
Mr Stanley spent a large part of today in his home with a plain clothes detective.
At about 3.15pm the officer emerged with four large brown evidence bags which he put into the boot of his car.
Ten minutes later he was seen carrying a laptop case and spare evidence bags.
Avon and Somerset Police said there had been no forensic examination of Mr Stanley's property, adding: "He is helping us with our inquiries."
Earlier, the witness was seen showing the police a distinctive army-style 4x4 truck in the driveway.
The 56-year-old took items out of the footwell and uncovered a large green tarpaulin from the rear.
As well as inspecting the green truck, which had "USA" and serial numbers printed on the side, the officer also looked inside Mr Stanley's BMW before they drove it away.
Mr Jefferies, who sports distinctive straggly white hair and was described by a neighbour as a "nutty professor type", was arrested at 7am on Thursday.
The bachelor was taken into custody just 24 hours after he claimed he saw three people leaving Miss Yeates's flat on the night she vanished - December 17.
Police tonight refused to clarify how long the new custody extension lasts for.
The suspect is a prominent figure in his Neighbourhood Watch group and taught English at Clifton College, just yards from his flat, from the early 1970s.
He took early retirement in 2001.
He is an enthusiastic activist for the Liberal Democrats in Clifton.
He is also a member of the Clifton and Hotwells Improvement Society (CHIS), which campaigns to conserve buildings in the area.
Resident Tony Buss, 51, said his arrest yesterday came as "a shock and surprise".
Another neighbour, a 26-year-old man who did not want to be named, said: "It's all been pretty scary, especially for my girlfriend as I'm away most of the week so it's been pretty scary for her to be home alone."
Referring to Mr Jefferies, he said: "We see him all the time on the road. He's a bit of a nutty professor type by the looks of it."
CHIS secretary RoseMary Musgrave said: "He's certainly an active member and does come to meetings from time to time. He's not a member of the committee, though."
In 2005 he was at the forefront of efforts to stop building work on fields near his home.
He led the Canynge Road Campaign Group to save the fields from development and wrote a series of letters to Bristol City Council outlining the group's opposition to the scheme.
Ray Lowman, who lives in a flat opposite the mansion where Mr Jefferies and Miss Yeates lived, said: "I'm amazed by it really but also find it quite disconcerting. "He is basically a pillar of society. One of the well-known familiar locals."
Councillor Trevor Blythe, who represents Clifton Ward for the Lib Dems on Bristol City Council, said: "We were absolutely flabbergasted when we heard he'd been arrested. I didn't know him particularly well, but it was very surprising.
"It's a terrible tragedy what's happened, and I'm just flabbergasted that Mr Jefferies has been arrested, and we await any developments."
Clifton College head Mark Moore said Mr Jefferies had at one time been the school's head of English and there were no disciplinary issues recorded against him.
"There was nothing in his record at all and he took early retirement, which he is perfectly entitled to do," Mr Moore said.
"When a new head of English came into the school, he decided to bow out at that point."
Yesterday, police took two cars away on low loaders - a silver Chrysler Neon parked on the street and a grey Volvo S40 which was on Mr Jefferies' drive.
Forensic officers spent the day in both Miss Yeates's flat and Mr Jefferies' property - taking away large brown evidence bags from both.
Officers continue to appeal to anyone who may have information to contact the Operation Braid incident room on 0845 456 7000 or call Crimestoppers anonymously on 0800 555 111.
A £10,000 reward is being offered to anyone who provides information leading to the arrest and conviction of those responsible.