A man is being sought in connection with a fatal fire which killed a seven-year-old boy in Deptford.
Joel Urhie's body was found in the bedroom he shared with his mother Efe Urhie at the house in Adolphus Street on 7 August.
Before he died he told his mother they were "going to make it together" out of the burning house.
Detectives have released CCTV of a man who was seen in a petrol station an hour before the arson attack.
Det Insp Alison Cole said: "The petrol station where these images were taken from is just a few miles from the Uhrie family home in Adolphus Street.
"We are asking for help to identify this individual as we would like to speak to him as part of our ongoing work - if only to eliminate him from our enquiries."
The CCTV images are due to be shown on the Crimewatch Roadshow on BBC One on Friday at 21:00 GMT.
The Met say the suspect is caught on camera with a petrol can which he fills with fuel he buys at a Shell garage on Shooters Hill Road.
Police say the man is known to have arrived and left the garage on a push bike.
Det Insp Cole added: "This terrible arson - one of the most horrific crimes I have seen in over 25 years of policing - claimed the life of an innocent child, a tragic loss his family will never get over.
"We desperately need the help of the public to bring justice for Joel's family."
For the first time, Ms Urhie has spoken about the last words she exchanged with Joel.
The 50-year-old explained how the pair were trapped in a bedroom and that she had planned to jump out ahead of him to cushion his fall.
She said: "He told me 'I love you Mummy', and 'we're going to make it together'".
On 11 August two men, aged 21 and 29, were arrested in south London on suspicion of murder, attempted murder and arson with intent to endanger life.
They have been released under investigation.
The Met say no body has been charged in connection with Joel's death.