A police officer was stabbed to death during the 1985 Broadwater Farm riots after he was set upon by an armed mob yelling "kill the pig", a court heard.
Nicholas Jacobs, 45, is accused of murdering Pc Keith Blakelock, 40, as the officer tried to protect firefighters tackling a blaze at the height of the unrest in Tottenham, north London.
The Tottenham riots of 1985 erupted the day after Cynthia Jarrett, a mother of a police suspect, had a heart attack and died when her home was searched in Thorpe Road, Tottenham.
Pc Blakelock was among a group of uniformed officers sent out without cover on the night of Sunday October 6 1985 to protect firemen putting out blazes.
They came across a "very large group" of rioters, many armed with an assortment of weapons, the court heard.
"Very heavily outnumbered and fearful they may become trapped both the police and the firefighters were forced to retreat. Outside the flats, as they ran for safety, Pc Blakelock and Pc Richard Coombes went to ground and were set upon to shouts of 'kill the pig' and the like.
"Pc Coombes was very fortunate to survive. Pc Blakelock did not. The attack on him was without mercy. In the ferocious attack his helmet came off.
"He was beaten and stabbed to death before his colleagues were able to force the attackers away.
"Pc Blakelock suffered something in excess of 40 stab type injuries and there appears to have been an attempt made to decapitate him."
Jacobs denies the murder. The trial continues.
More top news
ITV News witnesses the young victims of the world's worst humanitarian crisis amid an outbreak of the greatest spread of cholera ever known.
Prince Philip's final public engagement as a royal before retiring will take place in early August, Buckingham Palace has announced.
Passengers have been escorted off the Oblivion rollercoaster ride at Alton Towers after it stopped at its highest point.