There was quite a lobby in both houses regarding historic vehicles and Mot exemption.
A previous MP in Derbyshire was Greg Knight, he had a collection of cars from the 1930s to the 1950s
Iirc..
He and other motoring organisations pointed out that the brakes on an old vehicle could not meet the standards of the modern day. Jaguars like the E-type with inboard rear discs could not pass the test for the handbrake as more sophisticated Mot bays had accurate load measurement equipment not the old gadget that sat on the floor if the vehicle to measure brake efficiency on an actual road test. It was recognised that a rod braked car would never pass an MOT. This resulted in the need for wider exemptions not just Veteran Cars, Vintage needed a moving scale.
As regards to police stops the ANPR system is linked to the DVLA computer. The ANPR system does not access all the DVLA data on a roadside stop. If you check the Mot history of your historic bike on the DVLA system it will show as no current MOT, it does not have the facility to show the MOT exemption form where you make the declaration as to it's roadworthiness. An experienced Road Policing Officer will know about Historic Exemptions, with the reduction of Traffic Patrols this knowledge is no longer well known amongst normal patrol officers.