Media playback is unsupported on your device Media caption Video footage of a man with similar build to MI6 officer Gareth Williams was shown at his inquest

A third party must have been involved in putting MI6 officer Gareth Williams in the padlocked bag in which his body was found, an expert witness believes.

Peter Faulding told Mr Williams's inquest he would have been dead within 30 minutes of being put in the holdall.

The body of Mr Williams, from Anglesey, was found in his London flat in 2010.

The inquest was shown footage of two experts' attempts in which they struggled to lock themselves in a bag - but neither ruled it out completely.

These tests have addressed the crucial question of whether Mr Williams, 31, could have locked himself in the holdall in his bath or if another person must have been involved.

Footage played at Westminster Coroner's Court showed Mr Faulding trying to get into the bag in an empty bath.

Mr Faulding said that he had tried and failed to lock the bag from inside 300 times.

"I couldn't say it's impossible, but I think even Houdini would have struggled with this one," he said.

"My conclusion is that Mr Williams was either placed in the bag unconscious, or he was dead before he was in the bag."

Mr Faulding added that he had really struggled to get himself in the bag in the first place, and had had his feet resting on the bath and tiles, and his hands on the side.

He told the court that Mr Williams could not have got into the bag unaided without leaving marks and footprints, none of which were found at the scene in the flat in Pimlico.

But William MacKay, who said his military career made him adept at working in confined spaces, told the inquest that locking the bag was a skill that would have required training but that once a person had done it, they could not get out.

Mr MacKay and an assistant failed in 100 attempts to lock the bag from inside, and caused damage to the zip.

But he would not rule out that it was possible, adding: "There are people around who can do amazing things and Mr Williams may well have been one of those persons."

BBC security correspondent Gorden Corera, at the inquest, said: "This leaves the likelihood, which the police say they have believed since the beginning, that someone else was involved."

Computers examined

Later on Friday the inquest heard from Det Con Simon Warren, the police officer who had examined Mr Williams's laptop computers, memory sticks, CDs and DVDs.

He said that no security-sensitive information had been found, and also that there was no evidence files had been amended since Mr Williams's death.

Det Con Warren went on to say that about half of the internet use on the computers had been in the area of women's high fashion, including handbags, cosmetics, belts and gloves.

Image caption Mr Williams's colleagues from MI6 and GCHQ are due to give evidence

In December 2010, police revealed that they had found £15,000-worth of unworn women's designer clothing in six boxes at Mr Williams's flat.

Officers also revealed at that time that Mr Williams had visited a drag cabaret in east London four days before his death and had tickets to two more.

Det Con Warren told the inquest that the computers had been used to visit bondage websites, but he said this browsing was isolated and did not suggest an ongoing, active interest.

Det Con Robert Burrows said that Mr Williams's phones also had bondage websites in their browsing history, while a smartphone found on a table contained no data because the factory settings had been restored.

Following the conclusion of evidence for the day, coroner Dr Fiona Wilcox indicated that she might deliver her verdict next Wednesday.

Mr Williams has previously been described as a "world class intelligence officer" by his former boss at the government listening agency GCHQ.

At the time he was found dead he had been on a three-year secondment with MI6 in London and wanted to return to his role at GCHQ, the inquest has heard.