A small boy who appears in the latest Islamic State murder video is the son of a woman fanatic with links to the killers of British soldier Lee Rigby in London. The young boy, wearing camouflage and a black headscarf with an IS logo on it, has been identified as Isa Dare, the son of jihadist bride Grace ''Khadija'' Dare, from Lewisham, southeast London.The video shows the killing of five men accused of spying for the West while a masked man with a UK accent threatens British Prime Minister Cameron and vows that IS will occupy Britain. He then shoots one of the victims in the head.The footage revived memories of "Jihadi John", a British IS member who appeared in several videos in which hostages were murdered. He was killed in an air strike last year."It's desperate stuff from an organisation that does the most utterly despicable and ghastly acts and people can see that again today," Cameron said yesterday."This is an organisation that's losing territory, it's losing ground. Britain will never be cowed by this sort of terrorism. Our values are so much stronger than theirs. It may take a very long time but they will be defeated."After the killings of the five men, the young English-speaking boy, who appears to be about four or five, is shown saying: "So go kill the kuffar [infidel] right over there.''The US said in November that it had killed Mohammed Emwazi, or Jihadi John, who became a symbol of IS brutality after appearing in several hostage killing videos.The masked militant shown in the new video also spoke with an English accent"This is a message to David Cameron, O slave of the White House, O mule of the Jews," the man said in the 10-minute video released on Sunday."How strange it is that a leader of a small island threatens us with a handful of planes. One would have thought you'd have learned the lessons of your pathetic master in Washington and his failed campaign against the Islamic State," the man said.British officials said last year that up to 800 Britons had gone to Iraq and Syria, some to join I S . About half had returned home and about 70 were believed to have been killed.Grace Dare's father, Henry Dare, a minicab driver, said: "I was surprised when I saw the picture. It's definitely him. Of course I'm worried, but there's nothing I can do now."I'm not angry. I would never have expected it. I just hope someone is trying to bring them back."Asked about the police response to his daughter's radicalisation, he said: "I said they should watch her. She was a Christian, she went to the local Roman Catholic school. She was Christian until she changed. She fell under the influence of some people when she was going to the mosque."In July the mother posted a picture on social media of Isa, whose name is an Arabic form of Jesus, aiming an AK47 rifle that he seemed just big enough to lift.Dare, 22, who is of Nigerian descent, is understood to have been radicalised online then began attending the Lewisham Islamic Centre, where Drummer Rigby's murderers, Michael Adebolajo and Michael Adebowale, are reported to have worshipped.The mosque denies that they were part of the congregation.Dare's mother, Victoria, said her daughter changed her first name to Khadija after she began attending the mosque."I want her back in my life. She is my only child and the devil took her away."Dare made her way to Syria in 2012 and married a Swede known as Abu Bakr, who is thought to have been killed.She used social media to gloat about the beheading of US journalist James Foley and said she wanted to be the first British woman to kill an IS hostage.She has appeared in documentaries about jihadi brides...