Rover 25 cannot unlock the drivers door from the inside

Hello there ... If I manually lock the car from the inside by pressing the black cylindrical door locking button (not using the remote key fob) on the top of the drivers door - all doors lock - If i then pull the same door locking button up - to unlock the doors - nothing happens - the drivers door remains locked - I can manually open the passanger and rear doors by pulling the respective door locking buttons up - the only way to open the drivers door is with the key fob - Is this correct or is there a problem with the drivers door locking?

Thanks in anticipation ..