I'm sure the ones at Prescott launch had lockable, the key was inserted under a lift up tab

similar to this...
https://www.carbuilder.com/uk/94mm-locking-aero-fuel-cap-assembly-satin-aluminium

at least one of the last Roadsters had this version too

Last edited by CooperMan; 11/05/20 11:50 AM.

Jon M