second and third locks from the bottom are fitted with anti vandal locks, these require a BW key to open them and as the bottom gates are padlocks which hold the key captive until relocked makes bit of mucking about.
Brian In my view this is a counterproductive design, if your BW key is in a bunch fixed to your belt by a lanyard, in which case the only way to get back to the engine-room and move the boat was to lock the padlock on thin air, which is how it stayed as I couldn't leave the boiler again! BW would do better to trust boaters to act responsibly rather than trying to coerce them. Sean
