Re-Agreeing to public WiFi through login screens

On board a train whose WiFi has two screens (click "Join", click "I agree") I have no difficulty from macOS. I'm offered the two screens each time and I click to connect.

But iOS (11.2.6) appears to simplify the login by automating the clicks, after a past initial login. This in turn seems not to go well with this particular WiFi setup.

The WiFi icon indicates that there is a connection, but I can't ping outside.

Tinkering with the settings in the following ways to (re-)establish the connection does not work:

1. Turning WiFi off then on.
2. Forgetting then reselecting the WiFi network.
3. Turning off "auto-join" and "auto-login".
4. Clicking "Renew lease".

None of these make me go through the click-to-join-then-click-to-agree screens.

How do I connect through iOS to this (public, unsecured) network?