borrowed items and PvP worlds

I'm in the process of updating the RuneScape wiki and I have a few questions.

I know borrowed items cannot be taken to PvP worlds. What happens if a player has a borrowed item in their inventory and tries to log onto a PvP world? Does the game prevent the player from logging in until they have returned the item? If this is the case, what message does the login screen say? If not, does the item automatically get returned to the owner or does it go back into the borrower's bank and prevent the borrower from withdrawing it until they go back to a non-PvP world?

Thanks in advance.