How to make a thank you html page accessible only after form submission

How to make a thank you html page accessible only after form submission

I have a plain standalone HTML page with a regular HTML form, where the
action is to send registrants' details to our email marketing system. Once
they submit the form they get taken to another really simple HTML page
where there is a thank you message and a file download. Is it at all
possible to make the thank you page only accessible if proceeded to from
the registration page? I'm not sure if this is a logical question, since
there is no login or a database involved. I am also new to this so forgive
me if it's a silly question! Any help is more than welcome :)