the engine was ticking loudly and rhythmically at idle but sort of went away when revved. It was a metallic ticking but very pronounced. I had no idea what car it was at this point anyway the Mechanic* started to basically say it was knackered and was either piston slap 
a worn camshaft or a Hydraulic Lifter (coming back to earth now) he wasn't offering to do any work to the car which was commendable he just said it would be a big job and to take it to an engine specialist* as he only does basic servicing.Next minute goodbye's were said and the car pulled away, I opened my door a bit to see a Black D9 Estate drive off on a 51 plate (the car lives just round the corner I know). Now nothing ever goes wrong with the pistons or valve train on these so I'm thinking I could confidently tell the owner the Bottom Pulley is goosed and save the day? trouble is he'll freak out if I said I was secretly listening to his conversation with the Mechanic earlier so really need to try and catch him 'in action' as it were and offer advice.
My Bottom Pulley never got really bad but it was definitely the same kinda noise.
Opinions?
there was no-one around and I didn't want to look like an interfering nutcase....
)