A ROYAL Marine who shot an injured Taliban fighter in Afghanistan will be sentenced for diminished responsibility manslaughter on March 24 after his murder conviction was quashed by leading judges.

Five judges at the Court Martial Appeal Court in London ruled on Wednesday that Alexander Blackman, 42, from Taunton, Somerset, was suffering from an "abnormality of mental functioning" at the time of the killing.

They found that the 2011 incident was not a "cold-blooded execution" as a court martial had earlier concluded, but the result of a mental illness - an "adjustment disorder".

Blackman's murder conviction was overturned by the panel of judges, headed by Lord Chief Justice Lord Thomas, and replaced with a verdict of "manslaughter by reason of diminished responsibility".

The hearing on Friday March 24 will decide on the sentence he now has to serve.

Blackman was convicted of murder in November 2013 by a court martial in Bulford, Wiltshire, and sentenced to life with a minimum term of 10 years.

That term was later reduced to eight years on appeal because of the combat stress disorder he was suffering from.

The judges said on Wednesday that Blackman had been "an exemplary soldier before his deployment to Afghanistan in March 2011", but had "suffered from quite exceptional stressors" during that deployment.

The appeal court confirmed on Thursday afternoon that sentencing will take place on March 24 at 10.30am.