I though I had driven with the emergency brake on

This is due to one of two things. Either the caliper is sticking or the rubber brake line is swelling and not allowing the caliper to release.

The way to check this is to remove the caliper and retract the piston with a c clamp. If the piston pushes the fluid back to the master cylinder then the piston is ok. If not, it needs to be replaced.

Here is a video on how to retract a piston:

https://www.youtube.com/watch?v=j8YwfSKEzZo&t=29s

Here is a guide that will help with replacing the caliper if that is the issue:

https://www.2carpros.com/articles/brake-caliper-replacement

Below is the process from the manual on how to replace the caliper as well.

Let us know what you find. Thanks