A young clubber posted seven suicide letters to friends and family from a post box in Fulham before jumping in the Thames and drowning.
Joe Poynter had been talking about taking his own life in the months before he went missing from his home in High Wycombe, and told friends and doctors he feared he was losing his memory.
The 27-year-old entomologist, who was a regular cannabis user and had dabbled in a range of class A drugs through the clubbing circuit, disappeared in October from the home he shared with his sister and checked into the Montana Hotel in Gloucester Road, South Kensington, prompting an urgent police appeal to try to find him.
On the evening of October 27, he called Thames Valley Police, asking them 'not to waste any more police time' looking for him as he had already made up his mind to take his own life, and within five minutes would be jumping in the river.
He told them: "I've thought about it, I've taken months and months thinking it through, I made the decision a long time ago and now's the right time."
Mobile phone records gave Mr Poynter's last position as somewhere near to Westminster Bridge and St Thomas's Hospital, and a police community support officer on patrol in the area in the early hours of October 28 reported hearing cries for help from a man in distress, although a search of the water found nothing.
His body was recovered from the foreshore further upstream at Wandsworth Bridge, more than a week later on November 7. Police found Mr Poynter had strapped himself into a rucksack, which was tied firmly around his chest and contained a bottle of whisky and a 5kg dumbbell.
A post mortem examination gave the cause of death as drowning and found no evidence of Mr Poynter having taken any drugs.
At an inquest at Westminster Coroner's Court on Friday, coroner Dr Shirley Radcliffe said Mr Poynter was a 'bright, intelligent and capable young man' who had been troubled for a couple of years by the perception of memory loss, which may have been brought about by a combination of low mood, feelings of anxiety and cannabis use.
Recording a verdict of suicide, she said: "His mind was clear in what he was going to do. He had planned it and thought it through, even to the point of wearing a rucksack with a weight. Therefore I have no hesitation in recording that this was a death by his own hand."
Addressing Mr Poynter's mother, Katy Poynter, Dr Radcliffe added: "I wish to offer my deepest condolences. I can't imagine how terrible it must be for you to have to have dealt with that period when he was missing, but also the subsequent discovery of his body."
Thanking police for their help trying to trace her son, Mrs Poynter said: "They were absolutely brilliant and we've appreciated everything they tried to do for us."
