AN open verdict was recorded today on the death of art valuer Richard Cole, who was seen 'rolling' into an Amsterdam canal moments after being robbed of his mobile phone.

CCTV shots of 30 year old Mr Cole's final moments alive were tracked down by his half-brother Lee Thornhill, who gave the inquest a detailed description of what he had seen.

After hearing that tests revealed Mr Cole had been drinking and had taken drugs including Ecstasy before drowning in the Herengracht canal.

The Gloucestershire coroner Katie Skerrett said there were still unanswered questions about how he came to his death.

"Questions remain about exactly what happened and why he rolled into the canal in the way he did," she said.

"I have to come to an open conclusion. That will remain the case unless any further evidence is given to the UK authorities."

Mr Thornhill told the coroner that after his brother, who worked at Stroud Auction Rooms, was reported missing on January 25 last year he travelled to Amsterdam to help search for him.

He was shown CCTV of his brother making his way across the Thorbeckplein Square and talking on his phone, he told the inquest.

"He is clearly intoxicated, clearly drunk," stated Mr Thornhill. "He is ambling along, talking on the phone, concentrating on the call.

“We have pieced together from the timings that it was his girlfriend in America he was talking to.

"She was giving him co-ordinates as to where the taxi rank was. She was at home in Vegas.

"He then disappeared out of view of the local authority CCTV camera. But I went to a nearby hostel there and asked if I could look at their CCTV.

"That CCTV showed him being accosted by three gentlemen waiting at the end of the street.

“They started to lead him by his arm, leading him along. One guy was holding onto his arm every now and then and there were two more guys around.

"Richard still clearly had his phone in his hand. Having seen that, I went to a bank further along which had three or four different CCTV cameras and these showed Richard appearing to be upset by the fact he no longer had his phone in his hand.

"I can only assume it had been taken from him, judging by the gestures he was making. Knowing him well, I could see that.

"There was now only one guy with him. The other guys seemed to have gone off in different directions while the altercation was going on.

"I could see the guy go behind a car and then come out and check up and down the street. He walks off and comes back again.

"Then another altercation behind the car and then he comes out and sprints up the street away from it.

"A minute or so afterwards a taxi pulled up. The door opened and the driver had some communication with Richard. He stopped for about a minute and then drove off, leaving Richard on the floor.

"Richard can then be seen to roll a distance of six feet, possibly more, into the canal.

"I told police the position where Richard entered the water and he was found no more than 20 feet from there.

"When he rolled into the canal there was no-one else around him. It was a very unnatural roll.

“First, he tried to get up from the floor before the taxi came. He got onto one knee and then collapsed to the floor.

"The taxi came up and you can't quite make out what happened then but the taxi drove off and he seemed to roll vigorously into the water, quite quickly. It was not a drunken, side to side, roll - it was a definite roll."

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Mr Thornhill said he found it odd that Richard would have been drinking and using drugs that night because he was leaving Amsterdam at 8am and had a train to catch.

The coroner said she had been told by Dutch police that a suspect was prosecuted for the mobile phone theft but had since appealed and his appeal is currently going through.

She said a post mortem conducted on Richard's body after it was returned from Holland found he had minor injuries to his left arm and shin but they were not serious.

The pathologist gave cause of death as 'presumed drowning, potential intoxication' but could not be more conclusive than that.

Mrs Skerrett said a Dutch pathologist found evidence of alcohol, MDMA (ecstasy) and MDA (another amphetamine) in his system. He had also taken codeine.

The combination of substances could affect his co-ordination and orientation, 'increasing his propensity to fall into the water,' the report said.

The coroner said it was impossible to tell how the two factors - intoxication and drowning - interplayed with each other.

The inquest heard Richard, from Cam, was in the Dutch capital for only a night to sign a new business deal before travelling on.

He worked as a valuer of Oriental and Asian art for Stroud Auction rooms.