I flying regularly on BA on short haul out of Gatwick. There has been a marked reduction in the cleanliness of the aircraft interior over the last two years. It’s not so much the wear and tear, as the dirt which has built up. Especially on the backs of seats and on the metal parts between seats. Dust and dried liquid stains etc which have obviously been their longer than the previous flight. This includes the business class at the front of the aircraft, and does not seem to be a problem specific to any one aircraft type. This has not been a one off incident, it happens so regularly that I am now surprised when the aircraft is clean.