This is what I think anyway - Table Manners, the first play in the Norman Conquests trilogy (the first one I saw - which may have clouded my judgement) was probably nearly completed before the trilogy thing was thought up. I know that they say that the plays can be seen in any order but I'm not sure. Table Manners felt like a complete play, funny touching and sad, there are definitely gaps but you don't feel you've missed anything. Also the characters feel rounded and sympathetic, even if you don't completely like them.
Living Together felt a little like filler in comparison, other bloggers who saw this first (and only) hated it and I can see why. Characters seem nastier, not as well drawn, the plot feels scrappy and the jokes don't really work. That is, if you haven't seen Table Manners first (preferably an hour and a half before), then you see how the scenes bleed into each-other, how jokes in Table Manners are prefigured or paid off in this one and you feel that you are seeing different aspects of the characters. LT is still not as complete a play, it fills in gaps and has unnecessary silences where solitary characters are left doing very little.
Having filled in the gaps Ayckbourn seems to have decided to throw away most of the plot for Round and Round the Garden. Characters that were changed subtly in from Table Manners to Living Together get a more extreme makeover here. Also the minor characters of the six (from the previous plays), Tom and Ruth, get an entirely strange subplot of comic misunderstanding which really wasn't alluded to in the other plays. Round and Round the Garden also has what feels like an epilogue where much that was likely to happen after the end of Table Manners was overturned. For me the play was more complete than Living Together and possibly able to stand on its own but it wasn't quite as satisfying as Tables Manners.
This is rather long winded way of saying "see Table Manners first" whatever you are told to the contrary. The plays are not equal; there's a great one and two lesser ones rendered good by seeing the great one first.
Paul Ritter was fantastic when he wasn't being forced to be the "car bore" (I hate that character in Ayckbourn plays with the nasal voice, obsessed by cars, tools and the A147). Stephen Mangan made Norman sympathetic and sexy each time his character's boorishness was about to take over.
As a piece of nerdishness and to help me see the plays more clearly, I thought I'd write down the trilogy in chronological order:
Saturday 5:30pm - Round and Round the Garden - Act 1 Scene 1
Saturday 6:00pm - Table Manners - Act 1 Scene 1
Saturday 6:30pm - Living Together - Act 1 Scene 1
Saturday 8:00pm - Living Together - Act 1 Scene 2
Saturday 9:00pm - Round and Round the Garden - Act 1 Scene 2
Sunday 9:00am - Table Manners - Act 1 Scene 2
Sunday 11:00am - Round and Round the Garden - Act 2 Scene 1
Sunday 8:00pm - Table Manners - Act 2 Scene 1
Sunday 9:00pm - Living Together - Act 2 Scene 1
Monday 8am - Table Manners - Act 2 Scene 2
Monday 8am - Living Together - Act 2 Scene 2
Monday 9am - Round and Round the Garden - Act 2 Scene 2