It’s a common myth that real ale is “flat”. In reality, although it doesn’t display obvious bubbles, this is far from the truth. There should be an appreciable amount of CO2 dissolved in the beer, which gives it an obvious “bite” known as “condition”. This is evident even in gravity-dispensed beers with little or no head. At times when beer is not being served, a hard spile should be put back in the cask to ensure that CO2 builds up and does not just escape to the atmosphere.
Beer that is completely flat and has lost all its condition is extremely unappealing. Although in my experience this isn’t a common fault, it is one of the most difficult to complain about. Beer that is blatantly cloudy will generally be changed with good grace, and a vinegary pint is usually obvious enough for a complaint to be upheld. But if it’s just dull, flat and tired, all you can generally do is vote with your feet and go elsewhere.
When this regularly happens in what has been a well-loved pub, it poses a particular dilemma, to which I really don’t know the answer. I have never managed a cellar and wouldn’t presume to tell someone else how to do it, but I do know poor beer when I come across it.