Hi Simon,
Using the ?page=1 parameter with the Get a single topic endpoint will return the first 20 posts from a topic, and each subsequent page number will return up to 20 posts.
When there are no most posts available (EX: the page is too high and not valid), you’ll get a 404 response.
If you don’t specify a page number, the code will set a page number of 1, so ?page=1 is the same as not appending an explicit page to the topic request.
If you wanted to use this method to fetch all posts from a topic, you should be able to do so, even though it is not mentioned within the Discourse API Docs.