People seem to be having trouble reading the original joke, so here’s a replacement from Tim Vine, via my friend Dave:
So I was in my car, and I was driving along, and my boss rang up, and he said, ‘You’ve been promoted.’ And I swerved.
And then he rang up a second time and said, “You’ve been promoted again.’ And I swerved again.
He rang up a third time and said, ‘You’re managing director.’ And I went into a tree.
And a policeman came up and said, ‘What happened to you?’
And I said ‘I careered off the road.’