Don’t respond.
Appeal to the IAS with an expanded version of the original appeal, and rebut the nonsense from Napier that you were identified as the driver.
The IAS is not “independent” in any way and may also reject your appeal. Doesn’t matter, you’re in the right, ensure you continue not to identify the driver, communicate only in writing, and be prepared to stay the course which may include a court claim which you will defend.