I finish my short performance by pointing at an imaginary bathtub and raising my eyebrows in mock disbelief. There is nice, good-natured laughter from my tiny audience, who have been listening to this story, and waiting for this punchline, for the last several minutes. I relax, knowing I have done my bit. I have made my contribution to the party and now I can stand back and let someone else tell a story, safe in the knowledge that I will, for the rest of the evening, be known as the bloke who said that thing about his mate who fell into the bath.

But then one of them says, 'And then what happened?'

I am startled. I had not been expecting that. Traditionally, that story has always ended with me saying, 'And he fell into the bath!' and then pointing at an imaginary bathtub and raising my eyebrows, but now all eyes are on me. I am momentarily thrown and as I glance around at the expectant faces before me I don't know what to say.

'Basically,' says Colin, suddenly back from the buffet and witnessing my humiliation, 'his wife was absolutely furious with him ...'

The crowd begins to chuckle again. I turn to see Colin's face light up.

'Particularly as Steve was still wearing his pyjamas at the time ...'

The reaction is huge. The story has gone better than it has ever gone before. The idea of a furious wife and some wet pyjamas is almost too much for them to bear. One lady is doing one of those silent laughs where all they do is shake a lot with their eyes closed, and another gentleman just points at Colin and shouts 'HA!' before adding a little thumbs-up and walking off, waving his hands in glorious disbelief. Soon we are on our own and I turn to confront Colin.

'What did you do that for?' I say, shrugging in as angry a way as I can muster.

'Do what? I was helping you out!' he says. 'You were clearly struggling!'

'But you know Steve's wife wasn't there when he fell into the bath! And he wasn't in his pyjamas! What did you say he was in his pyjamas for?'

'It was just a little flourish,' he says. 'Just a little something to help the story along!'

'But the story didn't need helping along! It was fine as it was! He stumbled and fell into the bath! It's funny!'

'It's not that funny,' says Colin, with pity in his eyes. 'It's just a man falling into a bath.'