Mick, Andy and Paddy are sat at the top of a tower block they're are building, whilst sat on the highest girder they stop for lunch and Mick says:
'If my wife makes me roast beef sandwiches tomorrow I'm gonna through myself off this tower block' Andy nods in agreement and responds:
'If get cheese and pickle tomorrow, I'm gonna follow you down' Paddy looks at his sandwich 'If I get sodding jam again I'll be right behind you'
The next day arrived all sat there as before:
Mick; I said it, i meant it' roast beef. off he jumps...
Andy: Well I agreed... cheese and pickle again... he also jumps.
Paddy: I don't believe it Jam!!! again... he also jumps.
The difference is of course Paddy made his own sandwiches.