IOT : Connect iPad to Access point that has no internet access (ESP8266)

I have an ESP8266 board that is acting as an access point and web server. i.e. I can connect to it via wifi as if it was a router and it serves me back web pages. This will allow me to use my iPad to connect to a machine and check it status, look at logs etc using a standard browser. But the machine is NOT going to have internet access, it is local only.

This works fine on Windows and Android. If I connect an iPhone or iPad to it, it works for a little while, but as the ESP8266 does not have full internet access, the connection fails.

Is there a way to force an iPad or iPhone to connect to an access point that has no internet connection ?

Or

How can I fool the iPad / iPhone into thinking it does have an internet connection and so stay connected ? I can see that my iPad is sending some odd requests to the ESP8266 but I am unsure how to answer them.