That's not really unusual now. The E400Hs have been turning up on all Walkergate decker routes in the last few days as their five year funding stipulation to only appear on the 39 and 40 is about to or has already come to an end. Both Slayford and Walkergate seem to have a shortage of E400s at the moment as there are a number of MANs in daily use on the likes of the 12, 39, 40, 62 and 63. They could just be dupes but I don't think they are.