A four-year jail sentence given to a man who killed an Asperger's sufferer with a single punch in an unprovoked attack is to be reviewed by leading judges today to see if it should be increased.

Andrew Young, 40, died after being struck by Lewis Gill in Bournemouth, Dorset, on November 6 last year.

Three Court of Appeal judges in London will decide on whether the four years for an offence of manslaughter, which Gill admitted, is "unduly lenient".

The sentence, imposed in February at Salisbury Crown Court, has been referred to the appeal court by Attorney General Dominic Grieve, who will be presenting the case.

Gill, now 21, was also given a further six months - three months for an offence of handling stolen goods and a further three for committing an offence during the operational period of a suspended sentence. But only the four years for manslaughter is to be considered by Lord Justice Treacy and the two other judges.

CCTV images of the assault show victim Mr Young challenging a cyclist who was riding his bike on the pavement.

After one minute of discussion between the pair, Gill - an acquaintance of the cyclist - arrives at the scene.

The cyclist rides off and Gill appears to turn to follow him, but suddenly lunges towards Mr Young and launches a punch at his head.

Mr Young immediately falls on to the ground, where he lies motionless. Gill, of Sutton in south London, glances back at him before walking away.

The incident happened outside a Tesco Metro store in Charminster Road, Bournemouth.

Mr Young suffered a serious head injury and later died in Southampton Hospital.