Military personnel warned over rally in support of jailed Royal Marine

British military personnel planning to join a rally in support of a Royal Marine convicted of murdering an Afghan insurgent have been told they are not to attend "political protests".

Organisers are expecting more than 1,300 people to gather at London's Parliament Square on Wednesday in a public show of support for Sergeant Alexander Blackman.

The 41-year-old was given a life sentence after being convicted of murdering the wounded Afghan captive in Helmand province in September 2011.

The Ministry of Defence (MoD) confirmed servicemen and women had been reminded that they are not to attend "any political protests, marches, rallies or demonstration".

An MoD spokeswoman said: "Serving members of the military are given routine reminders that, according to the Queens Regulations RN, they are not to attend any political protests, marches, rallies or demonstrations.

"Any gathering which seeks to protest against a decision taken by the legal system or the Government falls into this category."

Former marine John Davies, one of the rally organisers, insisted the event was not a "political protest".

He told the Press Association: "There is a lot of support coming through from serving personnel who have confirmed that the MoD has issued orders that they are not to attend a political protest.

"However this is not a political protest. It is a show of support to one of our fellow Royal Marines."

Blackman, who was serving with Plymouth-based 42 Commando, quoted Shakespeare as he shot his victim in the chest at close range with a 9mm pistol after the Afghan had been seriously injured in an attack by an Apache helicopter.

Footage from another marine's helmet-mounted camera showed Blackman shooting the Afghan prisoner in the chest with a 9mm pistol.

Blackman was then heard telling him: "There you are. Shuffle off this mortal coil, you c***. It's nothing you wouldn't do to us."

He then turned to comrades and said: "Obviously this doesn't go anywhere, fellas. I just broke the Geneva Convention."

During the trial at Bulford Court Martial Centre in Wiltshire two years ago, Blackman was known as Marine A.

He denied murder, saying he believed the victim was already dead and he was taking out his anger on a corpse.

Blackman, of Taunton, Somerset was convicted of murder and jailed for a minimum of 10 years.

His conviction challenge was rejected by the Court Martial Appeal Court, although his minimum term was cut to eight years because of the combat stress disorder he was suffering at the time of the incident.

Wednesday's rally, which coincides with the anniversary of the founding of the Royal Marines, will take place from midday.