Definition of "oppo"

'I suppose you're referring to Fluker,' I told him, and he looked at me in stunned amazement when I explained that he was one of my old oppoes.

2012, Tony Orchard, Here's to our Far-Flung Empire

“It's all right, chaps, the decorator's come. This 'ere is me old ’oppo Ginger Vernall.”

2016, Alan Moore, Jerusalem, Liveright, published 2016, page 53