Learning to drive in your spare time is nothing to do with your employer. However, if it was paid by the employer on company time then it would be work, but your card would not be in I don’t believe (you are not delivering or collecting anything). Don’t mention it and carry on regardless, just like having a walk in the park. At some stage your licence would have to be sent away, which is the only thing remotely relevant to your employer.
The theory covers both classes.