Nodge68 said:

That's a governor smoke test, which isn't really needed on an engine with electronic fueling controls.
A modern diesel makes most smoke under acceleration, which is why the MOT regs now call it an acceleration smoke test. Most MOT test stations won't risk an engine failure for carrying out a pointless test governor smoke test, when a simple acceleration test is all that's needed.

Click to expand...

That's not what it says on the gov website

Hold the engine at full fuel position until a release prompt is given and immediately release the accelerator pedal.

kermit_rr said:

That's not what it says on the gov website

MOT inspection manual: cars and passenger vehicles - 8. Nuisance - Guidance - GOV.UK

Noise, exhaust emissions, engine malfunction indicator lamp (MIL) (sometimes called an engine management light or 'EML'), and fluid leak rules and inspection for car and passenger vehicle MOT tests.

www.gov.uk

Hold the engine at full fuel position until a release prompt is given and immediately release the accelerator pedal.

Click to expand...

I've asked my MOT tester in the past as to why they don't hold it at the governor any more. He told me that a governor test was the cause of too many engine failures, and isn't needed on the new smoke test equipment, so they don't do it.
Many modern engines don't rev to maximum RPM off load anyway, the wife's Audi only revs to 2250 RPM off load, which I suspect is a safety protocol built in to protect the engine.