Liverpool may have been a near miss. Go-Ahead were preferred bidders for Gillmoss in 2000 but then withdrew, and it eventually became part of Stagecoach in 2005. Then in 2013 Stagecoach bought Rock Ferry and Chester. So, we could by now have seen the big 4 in Liverpool! (OK, so had Stagecoach missed out at GM they might not have been interested in RF/CH but I don't want to let this get in the way of a good story!).
At Victoria we can see Arriva routes 2, 38 and 73 and Green Line route 757 among others, Go-Ahead routes 11, 36, 44, 170 and 436, Stagecoach Megabus and Oxford Tube, and First Green Line route 702.