He would have been 19, probably studying at college, perhaps with an eye on a future career as a PE instructor, for he was mad-keen on sports.

But any hopes and dreams belonging to Adam Regis were snuffed out four years ago in a savage knife attack which police brand as unprovoked, gratuitous and to this day apparently motiveless.

Now on the fourth anniversary of his death, aged just 15 years, detectives have launched a fresh appeal for information to track his killers. There have been 17 arrests of teenagers and young men over the years. But no charges have been brought.

The new bid is centred on the distinctive car used during the murder in Plaistow on March 17 2007 after the Kingsford schoolboy had a night out with pals and his then girlfriend at the cinema.

The getaway car used by the suspects is believed to be an old-style bronze mark II Volkswagen Scirocco. Registration plates ran from the old X-reg (December 1981) through to K (June 1992).

Despite extensive enquiries this relatively rare car has still not been found.

Det Ch Ins Stephen Clayman, from the Homicide and Serious Crime Command, appealed: “Someone must know who had access to a car like this in Plaistow at that time. It’s rare and distinctive and is a vital piece of the jigsaw towards solving Adam’s murder.

“It may have been borrowed by the suspects involved, it may have been driving around the area in the days leading up to the stabbing, it may have been disposed of afterwards.

Anyone with information is urged to come forward - there is a reward for information.

Adam, he said, was a thoroughly decent teenager who loved his family and had a reputation for being caring and thoughtful towards his friends. He was a reading mentor at his school.

“The murder was entirely unprovoked and for four long years Adam’s family, including his younger brother and sister, have had to live not only with their loss but the fact that no one has been brought to justice.”

It was just after 9.30pm when police raced to the junction of Boundary Road and Kingsland Road, Plaistow to reports of the stabbing.

Adam, who had been found lying in a pool of blood by his grandmother, died shortly after his arrival at Newham General Hospital.

A post-mortem gave the cause of death as a single stab wound to the chest. The knife used had a blade of at least 20cm and travelled through Adam’s right arm and into his chest, nicking the aorta of his heart.

That evening Adam had travelled on a bus with his friends back from the Showcase cinema in Beckton. He got off the bus at about 9pm at Romford Road in the area of Warwick Road E15 - about one-and-a-half miles from where he was found collapsed.

At some point during his journey home he was stabbed.

Afterwards two of the suspects were picked up by the driver of the VW Scirocco while two others fled north along the New City Road towards Barking Road.

From CCTV footage the vehicle is seen just before the fatal stabbing driving into Patrick Road. Two suspects - possibly Asian - got out and run off into New City Road towards Adam and his friend.

Had they already picked Adam out as their potential victim by this point?

Adam’s friend leaves him to go home and as Adam walks alone in Kingsland Road two suspects in hooded tops are seen walking on the opposite side of the road. Are these the males who previously got out of the car?

Two suspects are then seen on camera following Adam. The attack itself is not caught on CCTV but this immediately precedes the point when police believe Adam was stabbed.

CCTV then shows the suspects getting back into the car in Kingsland Road.

Two further males are seen in New City Road area of Jacobs House - a block of flats- running from the area.

Since Adam’s death, there has been a number of appeals for information, including a week-long series of events launched by detectives in 2008 with the support of Adam’s family. The events included a song and video by award-winning artist Chipmunk, school presentations and lorries clad in appeal posters touring Newham.

Anyone with information is asked to contact the incident room on (020) 8345 3775; if you wish to remain anonymous please call Crimestoppers on 0800 555 111.