Two forensic experts clashed in their opinions about the registration of a car caught on camera moments before Marsha McDonnell was brutally attacked, the Old Bailey heard.

CCTV footage taken from the H22 bus as the 19-year-old was waiting for the doors to open at her stop in Priory Road, Hampton, show a car passing from the opposite direction, which the prosecution alleges was that of bouncer Levi Bellfield.

The Old Bailey heard earlier in the trial that Bellfield arranged finance for a silver Vauxhall Corsa in November 2002 and sold his car on February 11, 2003 - seven days after Marsha was hit several times round the head with a blunt object and left for dead.

Experts were given the task of analysing a single still' image to establish if the Y-registration car and the one captured on CCTV matched.

Forensic analyst David Anley told the court he was sure the first letter of the registration plate on the footage could only be a Y or an X, disagreeing with a report written by fellow expert Andrew Waller.

Defending, William Boyce QC suggested that motion blur, lighting and picture compression could lead to limitless image distortions and that the absence of any other stills for comparison purposes meant the first character could be any number of letters, such as R.

Mr Anley conceded it was not ideal to work from one single still - the only one which captured the car's number plate due to the time-lapse style footage - but said: "A duck can not appear as an elephant but it can appear as a grouse".

After studying the footage concluded there was powerful' support that the car on the image was a Vauxhall Corsa, and limited support' that the two cars were the same.

The jury had heard earlier how Marsha was found by neighbours lying face down in a pool of blood after suffering several skull fractures in an attack.

Bellfield, 39, of West Drayton, denies the murders of Marsha McDonnell and Amelie Delagrange, the attempted murders of Irma Dragoshi and Kate Sheedy and the kidnap of Anna-Maria Rennie.

The trial continues.