Knocking/grinding noise on very gentle acceleration or feathering the throttle

[hgw]

New issue - a rather disconcerting knocking/grinding from the front (possibly passenger) side when applying the lightest of acceleration. Disappears when you increase acceleration or decelerate. Got my first MOT in a few weeks, so has anyone else had this?

 

[Alb]

Could be a stone trapped between the disk and heat shield. I've not experienced this on the MG5 but have on other cars.

 

[Noel]

Not sure if this helps, as you say this happens all the time.
However the discs are made of steel, and a thin film of rust forms on the surface, and this can be heard as a scrapping sound. But this is removed following a couple of applications of the brakes.