The worst excuse I have ever heard is:

• The wind blew the wrong way
• Leaves on the line
• The wrong kind of snow
• Yes, but I didn't inhale
• Categorically, er, no. Unless I was drunk at the time (old quote from Private Eye, but I can't find a reference)
• The lines of Venus were in the wrong juxtaposition
• No-one needs more than 640K of RAM
• The dog ate my homework

Regards,

John Davies