Timing tunnels

We left our mooring at half past the hour with an hour to get to Saltersford tunnel. Only three miles and we got there on time to go through. 

Several boats had come through on their time slot so we went on in to the darkness. A one way 424 yard small hole in the hillside.

Our bimini had been put down to avoid contact with the rocks and brick. There were more bends in the tunnel than the one at Braunston and being only one way proved more difficult to navigate.

The next tunnel at Barnton was longer but at least you can see through it. That one is not timed so we sounded the horn on the way through.

Is this another breach about to happen here?