Oh crikey Barry, I can't remember it was that long ago.. it was probably 2ish hours, give or take. A big chunk of the episode was already pre filmed, like scenes at the allotment etc, and at The Grand Hotel in Brighton at the end.
We were sat on the front row, and any time Del or Rodney weren't needed in the scene, they came and stood right by us.
I particularly remember the scene where Del is in the kitchen cooking bacon, talking to Rodney, and they had to do a fair few retakes, putting the bacon bacon back in the frying pan, as Del kept fluffing his lines.
it really was good ... but saying that though, whenever I watched Mother Nature's Son on the tv afterwards, for a short while it kind of 'spoilt' it a little bit, you know having seen 'their flat' as just a set, and not on the 12th floor of Nelson Mandela House, where I still wanted to believe it was! lol.