Mistake-Filled Joke

How many mistakes can you find in this joke?

So I was link surfing when I stopped to read this joke. Not only is it an awful joke, it's full of mistakes... which makes it funny(er). ------------ On New Year's Eve, Daniel was in no shape to drive, so he sensibly left his van in the car park and walked home. As he was wobbling along, he was stopped by a policeman. 'What are you doing out here at four o'clock in the morning?' asked the police officer. 'I'm on my way to a lecture,' answered Roger. 'And who on earth, in their right mind, is going to give a lecture at this time on New Year's Eve?' enquired the constable sarcastically. 'My wife,' slurred Daniel grimely.