A man who died after jumping into the River Thames in central London to rescue a woman handed his phone to a friend and told him to makes sure the police were coming before doing so.
Bernard Kosia told how Folajimi Olubunmi-Adewole made the leap after they heard a woman screaming.
He said she was crying for her life, shouting: “Help, I’m going to die”.
Mr Olubunmi-Adewole was one of two men who jumped in to save her, but his body was recovered about six hours later.
Mr Kosia and Mr Olubunmi-Adewole – who was known as Jimi to his friends – had been walking along London Bridge when they heard the screams.
They had just spotted the woman in the water when another man ran up to them, took his trousers off, looked at Mr Olubunmi-Adewole and asked ‘can you swim?’, to which he replied ‘yeah’.
“These are the things Jimi would do because he could swim, he’s a positive swimmer, we’ve gone to a lido, to a swimming centre and he can swim,” said Mr Kosia.
“Immediately after that he gave me the phone, he told me ‘Bern you stay here, you can’t swim, you make sure the police are coming’. I said ‘yeah, I will’ and then they both got in.”
Mr Kosia said he saw both men jump in and swim towards the woman.
“As I was on the phone I could hear Jimi screaming my name,” he continued.
“He was screaming my name, he was screaming my name. I couldn’t even see him. It was just pitch black, everywhere, and I was trying to see if I could see him.”
Mr Kosia said as he stood overlooking the river, all he could hear was his name echoing. Immediately after that the police arrived and sat him down.
The coastguard and the Met Police’s marine unit rescued the woman and the other man, but they could not locate Mr Olubunmi-Adewole.
The 20-year-old’s body was found several hours later at about 06:00 BST.
Mr Olubunmi-Adewole’s family have described him as “the deepest and most wonderful man” and said he deserved a medal for bravery.
His father Michael Adewola said: “I can’t bring him back but I want him to be remembered forever for what he did.”
He added: “It was just like him to want to always try and help others. He is a hero, and always will be.”
A campaign has been launched for Mr Olubunmi-Adewole to be recognised with a plaque on London Bridge.
Others have called for a plaque to be added to the Watts Memorial in Postman’s Park in the city of London.
John Price, senior lecturer of Modern British History at Goldsmith’s University and chair of Watts Memorial, said the groups that look after it had decided in 2010 that no further plaques should be added.
However, he told BBC Radio 4’s Today programme that he has recently had talks recently about turning Postman’s Park into an area celebrating civilian heroism.