Green’s Dictionary of Slang

pete tong adj.

wrong.

2000		Guardian G2 9: As rhyming slang for going wrong, ‘it’s all gone Pete Tong’ might have faded from the lexicon, but never has it been more true.
2001		K. Sampson Outlaws (ms.) 171: Here y’are, this is where it really does go Pete Tong.
2007		N. ‘Razor’ Smith Raiders 270: Things started to go Pete Tong.
2015		Guardian G2 3 July 7/1: It’s all gone a bit Pete Tong.