MI6 codebreaker Gareth Williams was probably killed but the "spy in the bag" case might never be solved after mistakes by investigators, an inquest heard.
Mr Williams's relatives attacked failures by secret services & police after a coroner ruled "many agencies fell short" in their investigation.
Fiona Wilcox said she was sure a third party locked the 31-year-old mathematics prodigy inside the red holdall, probably while he was still alive.
She criticised the 21-month investigation, saying it was unlikely the mystery "will ever be satisfactorily explained".
"The cause of his death was unnatural and likely to have been criminally mediated," she said during a two-hour narrative verdict at Mr Williams's inquest.
"I am therefore satisfied that on the balance of probabilities that Gareth was killed unlawfully."