Spy Gareth Williams 'may have locked himself in bag', yoga expert tells inquest Bag experts refused to rule out today 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 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. He said "many problems arise" in trying to pull off the task. "If it's in the dark that will compound the issue," he said. Mr MacKay said his assistant was very flexible and "if the task could be done, he is the person that could do it." Mr Williams' mountain climbing experience would have given him an advantage as it would have strengthened his fingers. But Mr MacKay added: "It was very painful to do it. You tend to move the zip with your finger nails, straggling about. It was very frustrating, fiddly, you just can't get the thing together. 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. 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. I would like to do it but... Mr MacKay said it was possible for someone locked inside the bag who wanted to get out to poke a small hole through the zip with their fingers. This would give them more oxygen and allow them to unlock the padlock as long as they had the key. "There was an option of saving oneself," he told the inquest. The expert said the holdall was not airtight, and as long as the person inside did not panic they would be able to breathe for some time. "If the person was in the bag willingly, then I am tending more towards the heat side being a problem than the oxygen side," he said. It depends on how calm you are in terms of oxygen intake. The inquest heard that one way of getting into the holdall would be to use the "baggage handler's technique" employed by thieves to steal from locked luggage. This involves breaking the zip apart with a pen, opening it as wide as possible, and then crawling inside and closing it again. But in tests the zip did not close neatly, leaving a gap between the two ends, and became damaged. Mr MacKay said it was "probably unlikely" that Mr Williams would have been able to do this successfully on his first attempt. There are so many intricate things to do. If he hadn't been trained, he wouldn't have had lots of knowledge, it probably wouldn't have happened," he said.