The mother of the first victim of serial killer Stephen Port vowed to “never shut up” after police refused to treat his death as murder, an inquest heard.

Anthony Walgate, a 23-year-old fashion student from Hull, was found dead outside Port’s flat in Barking, east London, on June 19 2014 after being given a fatal dose of GHB.

On Friday, Mr Walgate’s mother Sarah Sak told an inquest of her frustration at the investigation and how her son was regarded as just “a number”.

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Sarah Sak (second right), mother of Anthony Walgate, arriving at Barking Town Hall, London (Emily Pennink/PA)

She told jurors of her close relationship with her son, who had moved to Golders Green in north London in 2010 to study.

Ms Sak, who would talk to her son most days, was on holiday in Turkey when he was killed.

Having rushed home, she was initially told by an officer that he was found dead in the street, which was “unusual” but “not suspicious”.

Ms Sak told jurors: “I said ‘what do you mean unusual’.

“He said a FLO (family liaison officer) would be in touch and that was it. It was just minutes.”

The inquest was shown a report by the family liaison officer Detective Constable Paul Slaymaker detailing their first conversation.

In it, the officer noted that Ms Sak told him her son “likes to drink” and would “dabble in drugs – she thinks cocaine”.

Andrew O’Connor QC, counsel to the coroner, asked if it was an accurate record.

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The location outside Stephen Port’s former flat in Cooke Street, Barking, east London, where Anthony Walgate’s body was found (Emily Pennink/PA)

Ms Sak replied: “That’s an absolute lie. I never said that. I did say he liked to drink – because he did.”

On the death not being treated as suspicious, Ms Sak said: “I said to him, how come it’s not suspicious?

“People don’t just drop down in the street. And he said to me it was probably drugs.

“That’s when I just lost it with him. I said you can’t say that, it could be anything.”

From that moment the relationship went downhill, she said: “It was as though he had written it off there and then – it was probably drugs. He just wouldn’t listen to anything.

“I said Anthony was murdered. I will never shut up and I will never go away.

“He said he wasn’t murdered, it was unexplained.

“I said was he beaten up, was he shot, was he stabbed?

“I had a lot more input than was recorded and he said I was satisfied when I definitely wasn’t.”

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(left to right) Daniel Whitworth, Jack Taylor, Anthony Walgate and Gabriel Kovari were murdered by Stephen Port (Met Police/PA)

Ms Sak told jurors she was “furious” that she found out that Port had been arrested from the media and not police.

She described how she pushed police to find her son’s missing mobile phone.

“The fact Anthony’s phone had not been found, that was a significant thing, that somebody had obviously been involved and taken his phone.

“I said you have got to find his phone. I said to him ‘I’m not going away. I’m not going to shut up. Anthony was murdered. Something is not right about this’.”

She went on to complain to DC Slaymaker that she felt her son was being treated as just “a number”.

She told jurors: “I had said it would be quicker in Hull. I said he’s just become a number there.

“His exact words: ‘We get more deaths in a week here than you get in Hull in a year’.

“That was the thing that made me cry. It didn’t matter what I did, what I said. They were not going to do anything.”

After going to her local MP, she said DC Slaymaker was “really annoyed”.

“He said ‘how many times do I need to tell you, Anthony was not murdered’.

“I said how many times do I have to say he was.”

In September 2014, she found out about the deaths of Port’s second and third victims, Daniel Whitworth and Gabriel Kovari, and raised it with DC Slaymaker.

She told jurors: “I said how close they were and he just snapped at me.

“He said they are nothing to do with each other.

“One did not live in the area and the other was homeless.”

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A map showing the spots where bodies were dumped by Stephen Port during his 16-month killing spree (Met Police/PA)

On learning that Mr Walgate had GHB in his body, Ms Sak said she felt that he would “never have put himself in a position of taking GHB with a stranger”.

The mother said that she felt that being part of the gay community and involved in chemsex somehow explained her son’s death in the eyes of investigators.

And if he had been female, his death would have been investigated more, she said.

Ms Sak said the deaths of Mr Kovari and Mr Whitworth could have been avoided if police had treated her son’s death differently.

Referring to the inquests into the victims’ deaths, she added: “I realised after listening to these police for the last few weeks, no matter what I did, they would not have done anything differently.

“I was having sleepless nights. Could I have done anything more?

“But as I have listened to all of this, no matter what I did, they would never have done anything.”

Clair Dobbin QC, representing DC Slaymaker and other officers, said: “I suggest to you he was not the angry, dismissive, even homophobic person you have suggested in your evidence today.”

Ms Sak replied: “I do not agree.”

Over 16 months, Port killed a total of four young men in similar circumstances.

In 2016, Port was handed a whole life order at the Old Bailey after being found guilty of the murders.

The inquests at Barking Town Hall are examining potential failures in the police investigation and whether any of the deaths could have been avoided.