Exactly what constitutes a ‘bottle episode’ can vary according to the nature of the show. The fantastic episode Ice might be considered a bottle episode of The X-Files, for example, because it requires only one new set and a handful of actors; The X-Files regular cast and standing sets are so small that a true bottle episode would be nothing but Mulder and Scully talking in Mulder’s office (although actually, that sounds awesome). But technically, to be a bottle episode, excluding necessary framing devices or tags, the episode should feature regulars and recurring characters with no more than one guest actor, on standing sets only.

Of course, what really matters in a great bottle episode is the strength of the writing and the acting. The name could almost refer to the tendency for bottled up emotions to become un-bottled, secrets to be revealed, and generally for everyone to start shouting at each other around four fifths of the way through these episodes. In dramas, we expect to see emotional breakthroughs and revelations that will affect the characters for a long time to come (essentially, we want a teeny tiny Greek tragedy). In comedy – well, in comedy we really just want to laugh till we snort juice out of our collective noses, but it won’t hold together without some kind of emotional, character-based undercurrent.

All this pent-up emotion and necessary artistic creativity can make bottle episodes the best episodes of all – these ten are particularly successful.

10. ER, ‘Secrets and Lies’

The ship in the bottle: Four key characters plus new boy Gallant are stuck in a lecture theatre waiting for a seminar on sexual harassment.

Bottled up emotions? The sexual harassment seminar isn’t just a plot device for keeping these five in one room, coupled with an amusing way to start the episode – it’s also the biggest theme of the story, in which Gallant finds himself stuck on the edge of a complicated love quadrangle between Susan, Carter, Abby and Luka.