Lance Cpl. Joe Glenton - facing a court-martial for refusing to go back to the war zone - joined the march through central London on Saturday.
The 27-year-old told the crowd that as a soldier he expected to go to war. But Glenton said he "also expected that the need to defend this country’s interests would be legal and justifiable," and he doesn’t believe that is so in Afghanistan.
The Defense Ministry made no comment on Glenton’s participation. More than 220 British forces personnel have died in Afghanistan since the start of operations in 2001.