With the situation and claims in place, it’s just a matter of time before one of the sides declares war on the other:

Something interesting is that each war is considered a ‘phase’ of the situation, so until it ends, any war between France and England will be considered ‘the 1st Phase’, ‘the 2nd Phase’, and so on:

The Situation panel will also refresh when the war starts, so you can quickly check there everything related to it: