Spy 'may have locked himself in'
Experts have refused to rule out that MI6 spy Gareth Williams locked himself in his sports holdall unaided.
Video reconstructions showed a yoga specialist repeatedly fail the "frustrating, fiddly" task of pulling the zip within the 81cm x 48cm space.
But William MacKay - who said he made more than 100 attempts without success - said it was not impossible that the fitness-loving maths prodigy died without a third party present.
"I would not like to say that it could not be done," he told an inquest at Westminster Coroner's Court.
"There are people around who can do amazing things and Mr Williams may well have been one of those persons."
Several reconstruction scenarios were played of a man of similar build to Mr Williams getting inside an identical red North Face holdall.
While he had little problem curling his body inside the space, pulling the zip into position proved problematic.
Mr MacKay, an expert who has worked with the Army, suggested Mr Williams would have needed extensive training to have pulled off the act in the middle of summer and in pitch darkness. "I think you could continue to work on this for a long period of time," Mr MacKay said.
Mr Williams was found curled up naked in the bag in the bath of his flat on August 23, 2010. The family believe he had been dead for nine days.
Mr MacKay said he even tried to pull off the task in water and using chewing gum. He added: "At times we got reasonably close but I hesitate to say close enough that it's a task you can do even after a number of times."