Would someone tell Simon Cowell that his use of the adverb 'undoubtably' on The X Factor is a boo-boo for indubitably or undoubtedly; up there with Sarah Palin's 'refudiate' or Bush's 'misunderestimate'. Every week, in his tired homilies to contestants, he gets in an 'undoubtably' between his usual formulations 'I've got to tell you something' or 'Can I be honest?' Undoubtedly, a generation of debt-laden students is going around smashing up guilty buildings screaming undoubtably. And it's all Cowell's fault.
Not that online dictionaries can quite make up their minds on the matter. The Free Dictionary lists 'undoubtably' for indubitably even if Nanny Google offers the alternative 'undoubtedly' should you key in Cowell's word. Even my own spellchecker only accepts undoubtably if in quote marks.
A friend of mine once fell for a girl who used the word 'indubitably' - he was dead impressed by her articulacy. Please, Simon, try to keep up.