Detectives at Scotland Yard launched a murder investigation after the discovery was made on Wednesday morning and have not yet formally identified the victim.
The man’s body was spotted in the water by a member of the public near the entrance to the Islington Tunnel, by a houseboat-lined towpath popular with local residents, dog walkers and joggers.
A houseboat owner told the Evening Standardofficers asked him whether he had heard a shopping trolley pass by along the towpath.
“I’d gone to sleep at 11pm after being at the pub to watch the rugby and woke with the police banging on my window, he added.
“That’s when I found out the body had been found in a trolley. I think he was tied to it.
“There have been police around all day pulling things out of the river and divers down there.”
A spokesperson for the Metropolitan Police said officers were called shortly after 9am on Wednesday to reports of a “body submerged in the canal”.
“The body, believed to be a man, has now been removed from the canal and a post-mortem examination will take place in due course,” he added.
“Officers are now appealing for anyone who may have witnessed anything suspicious in the area in recent days.”
Anyone with information is asked to contact the incident room on 020 8721 4868, call 101 or Crimestoppers anonymously on 0800 555 111.