Come now. Tell us. Have you ever been caught staring folornly at a stone cold fox across a crowded tube carriage? Have you ever acted on a subterranean erotic impulse? Are you and your lover in fact sitting there now, fondling each other and fondly remembering the time you bumped bits on the Jubilee Line, laughed shyly and struck up a saucy conversation?

Qype wants to know, nosy blighters. So does Annie Mole (we hope the results might sit interestingly alongside her sightings of Tube Fashion Victims). They've teamed up to poke inquisitively into our Underground flirtations and fantasies. There's a cute little survey here, probing fancifully into what you have and haven't done, or wish you had, or whether you would. More importantly, they want to know where the hotties are. And the notties. Which is the sexiest tube line? This is vital information.

To encourage you shrinking violets to fess up your filthiest, they're luring you with a cheeky iPod Nano for one lucky participant - but you have to leave your name and email address for that. If you'd prefer to go incognito and smear your salaciousness all across this slinky survey, then you may.

Londonist will wait, smouldering, for the raunchy results.