These cars were equipped with the first version of a collapsible steering column.
The ignition lock is unique to these vehicles and uses a Lucas ignition switch (35893) which is no longer available.
The ignition switch is similar to the dashboard mounted switch used in the 1962-67 MGB.
This early switch can be substituted if the original wiring harness is reused by either soldering or using crimp push on terminals to attach to the ¼” male terminals of the early switch. Soldering would be preferred as there is very little clearance to attach push on terminals.
See attached PDF file for full walkthrough.