Two 17-year-olds have bee n arrested on suspicion of the murder of a man with learning difficulties who was stabbed in the heart.
The male youths are now in custody at west and north London police stations, Scotland Yard said.
Dean Mayley, 24, was stabbed as he walked along Ruislip Road, Greenford, west London, on February 7 at around 5.20pm.
Mr Mayley suffered from a development disorder which led to him having moderate learning difficulties and the mental age of a nine-year-old. His family say he was very vulnerable and easily led. It meant he rarely left home alone, except to visit relatives.
A post-mortem examination gave the cause of death as a single stab wound to the chest.
Scotland Yard has released footage of him getting off an E9 bus just under an hour earlier in Ruislip Road East, and walking towards The Broadway.
Detective Chief Inspector Matt Bonner said: "This was a vulnerable man who would have shown an unusual degree of trust in those who he came across and it is utterly sickening that he should have been set upon in this way."