The son of a pregnant British woman found dead in a Ghanaian hotel bathtub in mysterious circumstances has recalled the moment he was told his mother had died.

The body of Charmain Speirs, 41, was discovered in Koforidua in 2015, two days after her husband Eric Adusah, a Christian preacher from Ghana, had returned to the UK.

Local police arrested Mr Adusah on suspicion of murder but the case was dropped due to insufficient evidence and he has always denied involvement in her death.

A post-mortem examination in Ghana gave the cause of death as a heroin overdose and a second post-mortem eight months later in the UK found no evidence of assault.

Investigations into the death of Ms Speirs, who grew up in Arbroath, then came to a halt when a coroner recorded an open verdict at an inquest in Essex in 2016.

Now, a decade later a new BBC Disclosure documentary called 'Charmain and the Prophet' has reinvestigated the evidence and spoken to those who knew Ms Speirs – including her son Isaac, who talks about the moment he learned of her death.

In an exclusive clip shared with the Daily Mail, Isaac says: 'We were just sitting there for five or ten minutes in just silence. I remember my dad told me that she was dead.

'The first thing I said was 'you're joking'. He's like 'I'm not joking'. I just kept repeating 'you're joking'. No father should have to tell his son his mum's died.'

Isaac, 19, also accused Adusah of hitting him and his mother, saying: 'I could hear my mum screaming and crying. And he came into my room trying to hit me.

'My mum stood between me and him and he ended up punching her in the face. He called himself a prophet. What prophet would hit their wife? What prophet would lay a finger on a child? I don't think any prophet would do something like that.

'The way he talked to my mum, the way he treated her, he wasn't a prophet. He was an evil human being. He didn't deserve a fraction of the praise he got in that church.'

Isaac claimed Adusah controlled 'every aspect' of his mother's life including her phone, money, clothes, eating habits and 'happiness' – accusing him of 'dictating her life'.

The series, available on iPlayer, also claims to have uncovered a significant omission from Adusah's account of what happened at the hotel where Ms Speirs died.

Ms Speirs moved to Glasgow aged 19 where she worked in shops, restaurants and bars, before moving to Swansea aged 30 to study photojournalism.

She gave birth to Isaac in 2007 as a single mother and met Adusah in spring 2014 through a Christian dating website. They quickly married in September that year.

She became known as the 'First Lady' at Adusah's Global Light Revival Church, and had a celebrity status within the congregation as the wife of a 'prophet'. 

The church has three sites in Walthamstow, East London; Dublin and Maryland in the US - where Adusah now lives with his new wife and children.

But soon after the wedding, Ms Speirs confided in her mother Linda Speirs that their marriage was already in difficulty and she was planning to move home.

However, Ms Speirs flew out to Ghana and was found dead at the Mac-Dic Royal Plaza Hotel after she did not check out at midday on March 20, 2015, as scheduled.

According to police records, Adusah was the last known person to see her alive – and said they went for lunch before visiting the pool and returning to their hotel room.

Adusah claimed to have left the hotel after midnight to travel to Accra for a meeting at 6am before flying back to the UK, but Ms Speirs wanted to stay longer in Ghana.

However, a witness working at the hotel that night claimed two tall men, one of whom had a briefcase, arrived with Adusah late at night and went to their room.

The men were said to have stayed for up to one hour before helping Adusah put bags into his car – and Adusah left the hotel at 1am after telling staff not to disturb her.

Adusah never mentioned the men to detectives in Ghana, with police documents confirming witnesses reported the presence of three men.

Two of those men were tracked down and confirmed they knew Adusah through his ministry and were present that night – but claimed to have been praying in the room.

A third man appears to have never been traced. Adusah claimed he was meeting a reverend in Accra, but the BBC found this man – and he did not corroborate the story.

Ms Speirs's medical cause of death was recorded at Chelmsford Coroner's Court as acute opiate poisoning, but insufficient evidence for any possible conclusion as to how heroin entered her body meant the inquest finished with an open conclusion.

Adusah, who now lives in Maryland under the name Eric Isaiah Kusi Boateng, was contacted for comment by the Daily Mail through his church.

He told the BBC he suffered 'severe emotional distress' from the probe and attempts to question him, and 'profound personal trauma' after losing his wife and child.

The three-part BBC Disclosure documentary 'Charmain and the Prophet' next airs on BBC One on Monday at 8pm. The full series is available on BBC iPlayer now