RAF gunner Corrie McKeague, who vanished on a night out in 2016, had previously slept inside a bin and was a heavy sleeper when drunk, an inquest in Ipswich has heard.

Mr McKeague, of Dunfermline, Fife, was 23 when he disappeared in the early hours of September 24, after a night out in Bury St Edmunds, Suffolk.

He was last seen on CCTV at 3.25am entering a service area behind a Greggs store, and police believe he climbed into a bin which was then tipped into a waste lorry.

Chief Superintendent Marina Ericson, who became senior investigating officer from November 2017, said senior officers at RAF Honington, where Mr McKeague was stationed, reported him missing to police in a phone call at 3.42pm on September 26.

She said it was treated as a “high risk” case as he was in the RAF, his disappearance was out of character and at the time the major investigation team was also investigating reports of an attempted kidnap at RAF Marham in Norfolk in July 2016, which “was later discounted."

She said there were four overarching hypotheses when she became senior investigating officer.

These were: that Mr McKeague died following an accident; he died as a result of criminality; he remains alive but held against his will and unable to contact anyone; he remains alive and is deliberately staying away and does not wish to be found.

She told the inquest one line of inquiry was to look at Mr McKeague’s lifestyle.

She agreed with Peter Taheri, counsel to the inquest, that she said in a witness statement that “Corrie stated to a colleague he had previously slept in a bin”.

Asked for the source of this information, she said: “Two witnesses who were colleagues of Corrie McKeague.”

She said in her witness statement that Mr McKeague “was described as being a heavy sleeper when drunk”.

Asked by Mr Taheri for the source of this, she said: “Colleagues, friends, I believe some of the family statements made reference to how he slept when he had had a drink.”

She said that the movement of the airman’s mobile phone appeared to match the movement of a bin lorry that collected a bin from the service area where Mr McKeague was last seen.

She said that a hypothesis that Mr McKeague climbed out of a horseshoe-shaped area in Brentgovel Street was “thoroughly investigated” and found to be unlikely.

She said that 1,843 witnesses were spoken to during the investigation, with two people treated temporarily as suspects before both were told they would face no further action.

The inquest also heard that police interviewed a taxi driver after an anonymous caller suggested the airman had been sick in the back of a cab, before ruling out the driver's involvement.

Chief Superintendent Ericson said that officers twice interviewed a taxi driver during their investigation, both times after phone calls to police.

She said the driver told officers he did not recognise Mr McKeague and that he did not take people to RAF Honington, where the airman was stationed, due to a "previous bad experience".

An anonymous caller phoned the police rewards line a second time "100% certain Corrie threw up in a taxi of a named taxi driver on the morning he went missing", Ch Supt Ericson said.

The caller gave details of the firm the driver worked for, the colour of his car and the road he lived on.

"The caller said Corrie wouldn't be found," she said.

Ch Supt Ericson said that, when spoken to a second time, the driver "didn't deviate from his original account other than recalling he finished at 2320 hours".

"He recalled his last pick-up had been at 2300 hours," she said.

She said police "were subsequently informed" that the anonymous caller "was a friend of the taxi driver's wife".

"We contacted the original informant, the taxi driver's wife's friend," Ch Supt Ericson said.

"She informed police that on Monday, September 26, she had taken a lift from the named taxi driver.

"She stated she had noticed an unusual smell in the car and as the taxi driver had stopped to get petrol on the route he took out a package from behind the passenger seat stating it was fish that had gone off.

"Some three days later the friend again was in the car getting a lift with the same taxi driver when she noticed the car smelt much better and the taxi driver informed her he had picked up an airman who had thrown up in his taxi so he had been thrown out."

Ch Supt Ericson said the taxi driver theory was "discounted" and she was "as confident as I can be" about this.

She said there was not a call to a taxi firm from Mr McKeague's phone, with the last outgoing call from the airman's phone made at 9.42pm on September 23 to an RAF colleague, and the last incoming call from the same person at 10.44pm on September 23.

She said CCTV up until 6am on September 24 did not show a taxi entering the service area behind Greggs.

Police also interviewed a man who did a three-point turn in his car inside the service area and told officers he had been in Bury St Edmunds trying to get cash to pay his boxing coach.

CCTV did not show anyone in the passenger seats of the man's car as it left the service area, and his vehicle was in the service area for 51 seconds, Ch Supt Ericson said.

She said that, among the other alternative theories examined and ruled out by police, were a report that two people were overheard to say they had killed Mr McKeague after a robbery and threw his body in a bin.

Ch Supt Ericson said there was no CCTV evidence of Mr McKeague getting in a fight or being followed into the service area, and it was established that the two individuals were not in Bury St Edmunds that night.

The inquest, being heard with a jury, continues.