Anti-war protesters have set up camp outside an arms fair, being held at London's ExCel centre.
The DSEI event is described as the world's largest fully integrated defence and security exhibition, with nearly 30,000 visitors and 1,500 exhibitors.
More top news
The 20-year-old was found fatally wounded on Roth Walk, near Finsbury Park, north London at around 3am on Saturday, Scotland Yard said.
Police have arrested a man wanted in connection with a burglary at the home of pensioner Richard Osborn-Brooks.
The rally comes after it emerged that the Home Office destroyed thousands of landing cards documenting the arrival of windrush-era migrants