Sitting the right way round on a toilet seat....
In my past experience, even sitting the right way round on the toilet seat is not something i'd trust the inland revenue to do unsupervised.
Never give them originals of any document, never give them the benefit of doubt, never trust a member of staff that what they are telling you is true. Only ever give information in writing, never on the phone. Always make sure you can prove what you submitted, and when you did it.
I'm sure that some people in the HMRC are honest people, doing a difficult job with inadequately spec'ed IT systems - but as i havn't paid any bribes to have these people manage my tax affairs I always end up the other sort. I used to think they were just incompetent, but after a couple of events where i could prove that the person on the phone was blatently lying to me in the belief that i would not be able to prove otherwise, i know they employ some staff that are truly lying dishonest scum.
A/C as i am not dead yet, and so still have to pay taxes.