Henry Nowak's killer has had his life sentence increased on the day his bid to reduce it failed.
After stabbing the student, Digwa lied to police that he was the victim of a racist attack.
Attorney General Ellie Reeves referred the case to the Court of Appeal earlier this year, calling the sentence "unduly lenient".
Judges at the Court of Appeal ruled on Thursday that he should serve a minimum of 25 years.
Lady Chief Justice Baroness Carr, sitting with Mr Justice Nicklin and Mr Justice Wall, said: "A minimum term of 21 years did not adequately reflect the overall seriousness of the murder. It was not only lenient, but unduly so."
Mr Nowak's family said they faced a "life sentence of grief" as they welcomed the Court of Appeal's decision.
Jonathan Polnay KC, for the Attorney General, earlier told the hearing that Digwa had "repeatedly" used the knife against an "unarmed and defenceless stranger".
Mr Polnay told judges that Digwa "abused the privilege" allowing Sikhs to carry blades in public and that he "zoomed in on Henry's face whilst verbally gloating" as he filmed the aftermath of the attack.
Imran Khan KC, for Digwa, previously said that the sentence already reflected these aggravating features and called for a "materially lower minimum term".
Members of Mr Nowak's family were present for the hearing at the Royal Courts of Justice in London, with one relative wiping their eyes after the judgment.
He did not appear to react as his sentence was increased.
The Attorney General said in a statement: "The brutality and cruelty of this case horrified me, and I know that feeling is shared by the British public. I welcome the Court of Appeal's decision to increase the minimum term of Digwa's life sentence.
"My thoughts remain with Henry's family and loved ones at this incredibly difficult time. No sentence can ever fill the void left by his loss, and I hope this outcome goes some way towards bringing them the justice they deserve."
The murder case sparked violent protests after police body-worn footage was released showing officers failing to give Mr Nowak first aid and instead handcuffing him as he lay dying, despite him telling officers he could not breathe.
At the time, Judge William Mousley KC said the killer's attempts to lie to police and cover up his crime were among several aggravating factors that increased his sentence.
Mr Nowak's family say they have been "failed multiple times" by the police response to the 18-year-old's death.
In an interview for ITV Tonight, the family accused police of misleading them, giving changing accounts of their response to his stabbing and initially portraying him as the aggressor in the situation.
(c) Sky News 2026: Henry Nowak's killer Vickrum Digwa has life sentence increased after bid to cut it fails
PM reviewing decision to give UK military satellite system contract to US firm
Cristiano Ronaldo bows out from national team with emotional message
Married At First Sight UK will not return to Channel 4 following sexual misconduct allegations
'I'll die in prison for what I've done,' says man who drugged and raped wife in case likened to Gisele Pelicot
'Wild west' e-bike parking targeted - with possibility of locally set fees
James Matthews: Abdul El-Sayed's response to me felt like a misstep after stressful contest
Poundland owner turns to Thames Water creditors' lobbying firm as political heat rises
Third person charged after police officer shot in foot in Nottingham
