The Krays and their associates lured Jack 'The Hat' McVitie into a basement flat inside this East London Victorian semi. A 'party' was the ruse to lure the naive McVitie into a room, where a small group of underworld accomplices and the twins were waiting. Once inside he was punched by Ronnie Kray. Ronny had a shot glass in his hand and it smashed, opening up a gash across Jack's face. Perhaps symoblic of Jack's habit of drinking too much and talking too much.
Then (according to the courts) Reggie began frantically stabbing the stunned McVitie, who in a forlorn attempt to escape crashed through a small window. Upon making sure McVitie was dead the Krays left, curtly instructing their associates to 'deal' with the body. There were reasons the hit was carried out, but generally it was seen as something that could and should have been avoided. Jack's rather botched killing led to the Kray's downfall as there had been many witnesses.