Most of the metal on the first oil change with BMC's was from poorly washed out cylinder blocks after all the milling of faces and honing of the cylinders. Notoriously bad manufacturing of their engines. Most of it because of the time restraints for the costings of the engines. They were literally thrown together. The later mini's Allegro's (or All Aggro as they were known in the trade) Maxis, Marinas/Ital. Were the bane of my life. As all of it was so poorly manufactured. Triumphs well don't even go there. MG's were fairly well built.
I bought a Maxi even when I was in the trade ( due to someone writing off my car), biggest heap of Cr@p I have ever owned.
I worked at a BMC, Jag/Daimler, Rolls Royce dealership. What did I drive
A Ford