The first time you take your car to an MOT Test Station where it has not previously been tested, they may demand to see the V5C form as the emissions have been stated on this since the introduction of Euro II emissions as far as I understand - that is what out local Kit-car friendly garage told me.

If no emissions are stated then they resort to either Euro I namely 3.5% CO, 1200 ppm HC, according to year registration or no visible smoke for pre 1975, etc., as previously stated.

There is apparently a move to have a central database where all such information is stored, that can be accessed by MOT Test Stations.  No escape then! Try for full information.