Mrrzy,

'It is NOT enough to ask "What would YOU say if I asked you if this is the door to Hell?". If it were the door to hell, the liar would say Heaven and the truthteller would say Hell; if heaven, their answers would be reversed, so from that one question, you get no info.'

If the question is 'What WOULD you say....' the liar must also give an untruth as his answer. If he said 'I WOULD say heaven....' at that point he would be telling the truth. As he must always lie, his answer to 'What WOULD you say....' must also be a lie.

Gettit?

And 'cos I can't stand the tension any more and want to be a smartarse, the answer to my crossword clue:

E (13) = Senselessness