Mystery TFL ALX400

[2900]

Yesterday around quarter to five,ish at the merrivale Langley I noticed a TFL liveried bus turning right at the island towards dog kennel lane , all I got from the reg was LX53, it was ALEXANDER ALX400 bodywork with dual doors, destination box had a bright green blank display , I assume it was on private hire as it did have people on board, or the driver is very very lost.
Any ideas?

[Solo1]

No sure if decourcey  have any more ex London buses not yet in livery. Or could it be on rail work

[Cheese]

Maybe a little unlikely but LX53KAE is on the latest Ensign list as going to a church group in Droitwich, maybe a little far fetched to be in Langley but you never know.