hello, wondering if some might be able to advise on my current predicament.

After first parade this morning (checking levels etc. Have a normal start up & drive into work, happily tootling along. Engine had just about reached temp, and had covered about three miles.

I then hear a tapping sound and a huge amount of smoke emanating from the exhaust (seemed to be black grey and very thick).

Normally the engine is, and has been since the summer (when Project was MOTed) a little smokey, but nothing like this.

I feel it may be leading towards something catastrophic, but will confess this is my first Landy and first diesel. So experience is in rather short supply, any help would be greatly appreciated.

Could be a multitude of things, some really bad, holed piston, bent rod or minor like injector or head gasket.
I'd get a compression test done which will guide you or us where to go from there. Circa 400psi +
With all 4 cylinders reading close.

I had a similar thing happen to me a while back which ended up being the cam followers. Not an expensive job but took a bit of time needing the top half of the engine off. First thing to check is to get your rocker cover off and check the tappet gaps.

Sounds like something isn’t right. Tappet gaps is a good shout, any out of tolerance check the push rods for straightness, if something mechanical has failed these are the designed weak point. Compression test also good shout next step, just involves getting your hands on a tester.

I wouldn’t keep using it till you find the problem

Take the oil filler cap off with engine running to see if sump is being pressurised , should be some vapour blowing out but not like a steam train.

My money is on a failed injector.

Col