Hundreds of protesters have marched through London calling for a public inquiry into the death of reggae star Smiley Culture, as his nephew tells Channel 4 News the police "failed miserably".

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A crowd of around 600 people marched to New Scotland Yard to call for a public inquiry into Smiley Culture's death.

The reggae singer, whose real name was David Emmanuel, died of a single stab wound through the heart after four Metropolitan Police officers executed a search warrant at his home in Surrey on 15 March.

His family has been told he stabbed himself while making a cup of tea despite the presence of officers in his home. Smiley Culture's family responded to the police explanation of his death, calling it "bizarre".

Smiley Culture's nephew, Merlin Emmanuel, said the singer's funeral had been held on Friday.

Speaking to Channel 4 News he said: "(The) facts are Smiley died whilst under their custody, they had a duty of care to protect my uncle. They failed miserably. As a consequence you would expect at least a letter of condolence from the police force."

What I do know... is that Smiley would still be alive had they not gone and executed that warrant at his house. Merlin Emmanuel

He added: What I do know beyond reasonable doubt is that Smiley would still be alive had they not gone and executed that warrant at his house. I have my ideas as to what happened but of course its speculative 'cause I wasn't there.

"Let's look at the evidence, dig deep and see what we find. It beggars belief that they let someone go into the kitchen where there are utensils, sharp utensils, hot water and whatever else maybe in the kitchen to make a cup of tea. I've never heard of anyone whose house has been raided, who is being held as a suspect, afforded these kind of liberties. It beggars belief, it's hard to believe and of course I can speak for the family and the rest of the community, we don't believe it."

Smiley Culture pictured in 1985. (Getty)

The police watchdog the IPCC is investigating the case.

The IPCC's Mike Franklin told Channel 4 News: "If you put yourself in their position, people are clearly going to be very concerned about what happened, a terrible incident for friends and family of Smiley Culture. Our commitment is to make sure there is an independent investigation, make sure the family are told about the facts as we uncover them and make sure the findings of that investigation are made public, and that's what I intend to do.

My intention is that we will get to the truth... do not rush to judgement. Mike Franklin, IPCC

"I know what it feels like to be in those situations where communities are angry suspicious and upset and I've always been of the view that the community should feel free to express their feelings. It doesn't change anything in as far as the investigation is concerned.

"My intention is that we will get to the truth and I have already asked that people give us the opportunity to do the investigation thoroughly, which is my intention and do not rush to judgement."

Protesters marched from Wandsworth Road to Parliament Square earlier before holding a rally outside New Scotland Yard.

They chanted "No Justice, No Peace", played reggae music and carried placards reading "No more deaths in police custody" and "Who killed Smiley Culture?". Police said it was a "noisy but peaceful" protest.