Parents can finally say farewell but Milly's killer remains free

The words have been painted on to the side of a pay and display machine, a few yards from the spot where a car is thought to have pulled up alongside her. They read simply, "RIP Milly".

Plenty of traffic was going past on Friday afternoon last week, just as it was at the same time of day when 13-year-old Amanda Dowler – Milly, as she was known, made the short walk home through Walton-on-Thames that she would never complete. And again the question demands to be answered: How on earth did no one see what was going on?

On Friday it will be exactly a year since Milly's disappearance – an event so shocking, so baffling, so utterly at odds with the background of quiet prosperity against which it was set that the anguish it caused was, it seemed, felt by the entire nation. When, finally, six months later, Milly's body was found in a wood some 20 miles away, it was the outcome to which everybody had all but resigned themselves.

Now, with a huge police investigation having yielded nothing but false leads, Milly's family – parents Bob and Sally, and 17-year-old sister Gemma – face an anniversary that will be all the harder to bear for the knowledge that the killer is still out there. But the moment also represents an opportunity – chiefly, for the Dowlers, to give Milly the funeral that the investigation has so far denied her.

For Surrey police it is a chance to catch the public's attention again. People leaving Walton-on-Thames railway station on Thursday afternoon will be stopped and asked if they recollect anything that might give the investigation a new impetus. Police will also question people at Yateley Heath Forest in Hampshire, where Milly's remains were found.

And at Milly's school, Heathside in Weybridge, classes will hold assemblies at which Milly will be remembered, with educational psychologists on hand to talk to pupils who have still not got over the death of their friend. "It will always be part of the history of the school," says John Ambrose, an education officer with Surrey County Council. "But we've tried to draw a line under it while at the same time allowing us to remember Milly. It has been traumatic for everybody, but at the same time the school is a very strong community."

Instrumental in devising the assemblies and helping the school through the past year is a local vicar, Nick Whitehead. Mr Whitehead is not only a parent at Heathside but also brings to bear the experience of having conducted the funeral of Sarah Payne, the eight-year-old whose abduction and murder in 2000 was another very public tragedy. "I'm not alone in this situation so I wouldn't want to overplay it," he said. "I have had a colleague who was chaplain at Dunblane. But inevitably the one process has informed the other."

The Sarah Payne case did at least end in a conviction. What hope of the same in the Milly Dowler investigation? The key to the mystery still lies in her last known movements, the Thursday afternoon when she had left school and caught the train home with friends. It is two stops from Weybridge to Hersham, the station closest to where Milly lived, but she got out at the first stop – Walton. Although it meant a longer walk home, other friends were getting off there and she went with them to a café on the platform where they bought some chips. Using a friend's mobile, Milly phoned her father, an IT consultant who was working from home, to tell him she would be home in half an hour.

Video footage from a CCTV camera on the side of a nearby building provides the key evidence of what happened next. It shows a figure – in all likelihood Milly – a few yards from the station and heading towards her home. She is apparently talking to the driver of a car. The camera is on an 84-second rotational sweep, and the next time it comes round, Milly – "sensible and not at all gullible" in her mother's words – and the car are nowhere to be seen. And in spite of a police investigation which has involved thousands of interviews and more than 100 officers, not one person has come forward to say that they saw Milly getting into the car, still less that they saw any sign of a struggle.

Meanwhile, life has had to go on for the Dowlers. Mrs Dowler, a teacher at Heathside, has not been back to work since her daughter's disappearance, and instead has concentrated on setting up a charity – Milly's Fund – that promotes safety for children and teenagers and has close links with the Suzy Lamplugh Trust. For Gemma Dowler, the loss of her sister meant she was unable to sit her GCSEs last summer. She was assessed instead, left school, and is now studying for a GNVQ at a local college.

"I don't have feelings of revenge," Mrs Dowler has said. "Not yet at least, because there's no one to blame. But I don't know how I'll feel if they find Milly's killer."