Five months earlier, the killer had been freed from custody over possession of a knife and drug dealing.
Nachev is believed to have targeted Hakim, also 18, in a row over a girl. He had previously punched Hakim and is suspected of stabbing him in the arm in a subway two months earlier.
When Nachev was arrested, police found he had used his phone to research youth stabbings prior to the fatal attack and had looked up zombie knives and samurai swords.
The victim’s mother, Saranba Sillah, said: “Hakim was stolen from us in an unprovoked, brutal, malicious and cowardly attack.
“The murder of Hakim has torn apart the very fabric of our family. In addition, this senseless attack is a painful reminder of the knife-crime epidemic that continues to ravage our society… This a reminder that the betterment of a society is not a duty to be left to some, but a responsibility to be shared by all.”
Nachev, who claimed self-defence at trial, was convicted of murder at Isleworth crown court yesterday and will face a life term when sentenced on September 7.