Thanks @Teodor. I had already tried that and it didn’t make a difference. However, I’ve now spotted that this was in my layout file:
<meta name="ac:route" content="/">
I’m guessing because it was previously using the old routing method. I’ve removed that line and it’s now working.
If these two aspects, adding the line to the content page and removing it from the layout page, could be automated then it will save a lot of head scratching.