Police last night revealed a 17-year-old was attacked with a machete in Northampton's McDonald's last month.
Investigations into the attack in the Drapery — codenamed Operation Clay — are still ongoing after four teenagers were charged following the incident on October 14.
Two 17-year-old boys and a 16-year-old boy appeared in court charged with Section 18 Wounding with Intent, Violent Disorder and being in Possession of an Offensive Weapon.
Another 17-year-old boy has also been charged with Section 18 Wounding with Intent and Violent Disorder.
None of the accused can been named due to their age.
Armed police responded to a 999 call of a violent fight at McDonald's around 4.30pm on October 14 and were on scene within four minutes as horrified diners fled the restaurant.
A Northamptonshire Police spokesman later said a 17-year-old had been the victim of a knife attack and sustained injuries which were "not life-changing or life-threatening".
Police are appealing anyone who witnessed the incident to call 101 using the reference Operation Clay. Alternatively, anyone with information who wants to remain anonymous can call Crimestoppers on 0800 555111.