The hammering didn't work. I got the spanner and managed to get the top loose. But unfortunately the hatch still didn't close. I couldn't get the bottom loose, but help was at hand: the ratcatcher! He tore the bar off and the hatch could close. I locked one side of the hatch, but the other side didn't have a lock anymore. In the end we used a piece of rope. I had to go back to the mechanics to get it fixed properly. In the process I was home nearly an hour and a half later. My hands were filthy, I was quite cold and my clothes need a wash!
On the bright side: nobody got hurt and no vehicles were damaged.
PS: the ratcatcher is someone who goes around the countryside, especially near dykes and levies, to check on holes made by muskrats that might damage the structure ànd cause flooding!