On further investigation, this is a very complex feature to install and get right. Microsoft strongly recommend that it is installed in a cluster in case a node is lost. Otherwise, recovery is very difficult, if not impossible.
While it isn't the answer I wanted, I have since found that you can interrupt the Windows 11 installation process and insert some registy keys that will allow you to install it without TPM. Search for 'Windows 11 LabConfig'.
Not recommended for production or critical usage, but allows you to run Windows 11 for testing purposes at least.