Leon Scott, 41 and of Drayton Close, Ilford, stabbed the victim multiple times during the attack on Ley Street in the early hours of Monday, 27 November last year.
The 31-year-old victim was speaking to two people outside the shop when Scott launched his attack.
A member of the public intervened and helped administer first aid before paramedics arrived.
Two knives were recovered from the scene.
Scott was arrested a short time after the incident and charged with attempted murder.
The victim has suffered lasting nerve damage to his arm.
Acting Detective Sergeant Jeremy Collins, of East Area CID, said: “This was a frenzied attack which was unprovoked and came totally out of the blue. It was a random attack by all accounts.
“The level of violence used was absolutely shocking, and amongst the worst I have seen. The scene that unfolded that morning is the stuff of nightmares, and the victim has endured lasting physical injury and psychological trauma as a result.
“The victim was stabbed 30 times, and it is very fortunate that he was not killed. The member of the public who helped stop the attack deserves particular recognition.
“Scott was quickly identified as a suspect, arrested and taken into custody. He has never shown any remorse, and is a dangerous offender.”
Scott is due to be sentenced next month.Tags: Ilford
© TIME107.5fm 2015-2019. All rights reserved.