A Heathrow Border Force officer suffering from multiple sclerosis accidentally drowned in the bath after consuming almost three times the drink-drive alcohol limit, a coroner ruled on Wednesday.

Claire Parry told a platonic friend who lived with her that she was going to take a bath at her Iver home when she was so drunk that she was in danger of falling into a coma.

However, the coroner’s investigation could not determine when the mother-of-one had drunk the alcohol, as a key witness, Steven Hall, had changed his address and failed to attend the inquest.

The 45-year-old woman had spent the afternoon on September 9 last year sitting on the kitchen floor, saying it was the only place she felt comfortable and asked Mr Hall, a fellow divorcee who she had met on Facebook, to run her a bath.

In a written statement, Mr Hall told the inquest: “I assumed she had suffered a bad turn or was ill. I went upstairs to run her a bath and when I told her it was ready, she moved along the floor to the stairs. She was struggling with her movements. Claire took herself upstairs to have her bath.”

Mr Hall then went to buy some wine. Before he left he had called up to Ms Parry to ask if she wanted anything and she had replied: “I’m alright sweetheart.”

When he returned to the house in Market Lane he again had called up to Ms Parry, who told him she was getting out of the bath. Then he heard noises he said sounded like movement and assumed she had gone to bed, so he kept watching television until after midnight.

The assistant Berkshire coroner heard that when he went upstairs he discovered the bathroom light was still on and after investigating, found Ms Parry in the bath with her mouth and nose submerged.

The inquest heard that the Border Control officer was diagnosed with MS in 2013 and her mobility had been limited as a result, to the extent that she had at times relied on a wheelchair.

Ms Parry had been taking a mixture of drugs to reduce her tremors and anxiety, as well as anti-depressants but the toxicology report revealed she had stopped taking two of the drugs.

In a statement to the inquest in Reading Claire’s mother, Lesley Riding, said: “Claire was very excited about her daughter’s imminent 16th birthday and wanted her daughter to move in with her. Claire had everything to live for.”

Ruling Ms Parry’s death was accidental, the assistant coroner, Alison McCormick, said she was also disappointed that Mr Hall had failed to attend and that she would have served a summons upon him if officers had been able to determine his address.

“It seems to me that on the balance of probabilities it is more likely than not Claire accidentally drowned in the bath. Claire was in a fairly bad way with her multiple sclerosis at this point in time.

“She had clearly had a large amount to drink and I also take into account that she was probably not taking all of her medication.”