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After sentencing, Det Insp Richard Mackenzie from the Met Police said Zou was "one of the most prolific predators we have ever seen".

Det Ch Insp Stuart Brangwin, from Thames Valley Police, said both Mr Latter and Jake, who was 17 at the time, "gave us a really clear account of what happened – we don't normally get that".

Mr Latter "himself suffered something like 20 knife injuries to his neck alone and somehow survived", said Det Ch Insp Brangwin.

He gave some unsolicited comments outside of the formal interview in which he simply said he went "loopy", "lost the plot" and "lost his cool", said Det Ch Insp Brangwin.

"What is clear from the evidence presented by other witnesses is that drugs featured in both his and Jo's life and their lives did involve the use of cocaine and cannabis," added Det Ch Insp Brangwin.