Marques Walker (left) recorded footage on a phone smuggled into his cell following his arrest for stabbing Jermaine Cools, 14, (top right) to death in Croydon in November 2021, tormenting his family
Marques Walker, 17, and Vanushan Balakrishnan, 18, were awaiting murder trials for separate stabbings when they were placed in the same cell block at Feltham Young Offenders Institute.